you might consider the ones that sit in the room and use a vent hose type thing that goes out the window which would require a much smaller opening in the window and I think they do come with the adapter that goes in the window. An advantage is that this type is portable and can be moved from room to room if needed.
You would be looking for a casement style window opening when you are looking for a window unit they are made differently than the regular window type.
If you google casement window air conditioners you will find many.
For the portable type here is an example of one at amazon and there are pictures of how the window kit fits in. Be aware some of these type have a water bucket that has to be emptied some don't that could be a consideration.
HONEYWELL Portable Air Conditioner

I had a small window ac unit in my master bed room in my other house because I like it really cold in my bedroom plus it allowed me at times to turn off the big ac that was just used for the bedrooms and only use the small one in my room since it was the only bed room used. That little ac could freeze you out of there and it was a huge bedroom/bathroom area, it was around 5000btu.

I meant to mention on my window I got a lock down bar that goes in the window frame that will keep the window from being forced open, I have them on my windows here too. It works much like when you put a broom handle in the tracks of a slider door they can try to slide it open but the bar in the track stops it.
So the most they could do is possibly tear out the ac or window vent but the window could not be opened any further, if the ac is big then they could crawl in through the opening where it was if they managed to rip it out. That is another advantage to the portable one you only have a small opening in the window to deal with.

I have these small ones on my windows here
High-Security Sliding Window Lock - 3-Second Installation

for the lock bars do a google search for window lock bar to see a selection.

I went with a portable one for the new house this summer. The house is supposedly Centrally AC'd, but it's not efficient, and I can't see paying to cool an entire house for 2 people (one of which is usually outside or messing around in the garage--LOL).

The portable ones aren't really all that portable--they're heavy, and a bit of a pain to unhook and rehook up to the next window BUT I like the fact that there is nothing to screw in anywhere (no extra holes in my house), and in a pinch you CAN move it from room to room if the need arises.

They come in two versions--one evaporates the condensation, with the other, you need to position a bucket under the hose and empty it a couple of times a day. That may be a consideration for you.

Really, though, even if it's not going to be moved, I'd go with a portable unit everytime--just makes sense to me to have more options and fewer holes drilled into the house. As to the exhaust hose? I think you'd just turn it sideways and it would fit in a side-sliding window.

If they have a better window in the living area of the apt put it there and set a box fan in the hallway facing into the bedroom. Then fix the window so it can't be opened, a stick cut the right length or bolts holes through both windows on one side and put a long bolt through the hole. That is what we did when we only had window units. Unless they have changed the window units, they can't be removed from the outside.

As a matter of fact we used the bolt method for making the rental safe. We drill the hole through both sections of the window, with the window open about 5 inches then when a bolt is put in the hole, you have a breeze way and no one can raise the window but they can be removed to open wider. My Mom did that to her house too.

Sliding windows are not casement windows. Casement windows are the crank-out type. I have the sideways sliders so I know what you're going through. There's more work to putting a unit in with these but I like the windows so it's something to live with.

Most new a/c units are much quieter than before. My old unit died and I bought a new one. Much quieter, albeit less powerful.

Security is an issue with any window unit. Someone determined to get in can and will. However, any available window is also an opportunity to get in as is a door. One or two good kicks on a wood-framed door and that door is open. Wooden frames are not secure.

I put my a/c unit in a room in which I don't sleep, then set up fans to circulate the air. Much less noise. If it gets really hot where you're at you might consider 2 units. A/C units don't have to be expensive. You can buy them for under $75. The smaller the unit, the cheaper, but, the benefit is that they're much easier to put in and take out as they weigh less.

Everyone I've talked to about the "portable" units, that use a dryer vent hose seem to agree that they're far less efficient, much more expensive (probably 4-5 times) and not generally worth it except for extreme situations. Some have an evaporator for the moisture, which essentially puts the moisture back in the air, or else you're dumping a small container of water frequently if it's humid weather. A window unit of course drains outside when installed properly.

Putting an a/c unit in isn't too tough. Remove the screen. Something on the bottom to protect the window frame and it should match the width of the a/c unit. It should be weather resistant, even if just put in a plastic bag. I then close the window around it and put in a blocker for the window opening. I like using the corrugated plastic for starters, cut to fit the opening snugly. Old campaign signs work great. They also give some insulation. I try to place it in the window tracks then tape it up good with box sealing tape and/or duct tape. Then another layer of something over that. Another sign or some cardboard, again, will give insulation too. Close the inside window onto it and then I use an old rectangular chair cushion in a plastic bag stuffed in the opening above the a/c. More insulation and seals out the weather. Then it's to seal by the a/c unit itself. Bubble wrap and chunks of foam rubber wrapped in plastic bags stuff in there and stay in place.

The better taping job you do, the more "secure" the window is. They won't be able to slide it open. My old one had the flaps on the side that stayed inside so it couldn't fall out or be pulled out by someone outside. The new one isn't that way - I didn't put those things on because I wanted it easier to install and seal.

Mine has a remote control which is very handy since I don't really go into the room. But that's a little more expensive.

For a little extra security, cut a rod of some type to brace against the window and the frame, much like the broomstick in the sliding door feature.

FWIW, my old unit was an 8800 BTU unit, the new one is something like 5500-6000. I cool the bedroom it's in, hallway and large living room with it and we had 100°+ temps and over 80° dewpoints this year. So I'm pleased with the performance of the smaller unit.

Another consideration is the windows. Put some insulation on there. Insulated drapes make a BIG difference. You can make some simple window coverings though for the really hot days to help by simply using quilts and/or bubble wrap. If you're allowed, hang some of those rollup shades outside to block some of the sun and heat out. We hung some of those on my old GF's apartment balcony to shade her sliding door and it worked nicely on calm days.

Another option is to help the a/c unit. Get a dehumidifier and use. Once you remove the humidity it's easier to cool the air, therefore the a/c unit works less and a higher temp will be more comfortable. Most will hold a gallon or more so they don't have to be emptied as often. They're also pretty quiet in operation.

are you costco memebers? they carry the portable one...however it's seasonal in the store..i havn't checked to see if you can get ine online out of season...

I said that the search would be for casement window air conditioner. They are displayed as slider/ casement style. They are combined within one search term.
As is shown here

Here is a link that might be useful: Search results

A few years ago before I got my new kitchen windows I had casement windows and I bought a floor model air conditioner. It did a great job, it is not something you would be able to move very easily as you have to fasten in the vent hose to the opening and have the window opening completely covered with something. They used plexi glass on mine. It does have a container built into it that you have to empty at least once a day depending on the humidity. There was a way you could hook it up to a drain if that was possible but we did not do that. I bought mine used at a garage sale and it was like new. I still have it and plan to keep it, but use a regular window air conditioner now that I have casement windows there.

Sue