Adult or child?

https://arcticzone.com/products/9-can-titan-deep-freeze-zipperless-cooler

We use the hard pack blue ice.

We bought a bunch of these at Academy sports. They are thin and small so they are easy to fit in.

https://www.academy.com/shop/pdp/igloo-maxcold-ice-blocks-4-pack

Along with the big blue ice hard packs at Academy. They have the yeti hard pack blue ice also.

If you put the lunch items in the fridge the night before so that they can be chilled by morning, that and a frozen water bottle should be more than enough in a small insulated bag to stay cool. Put a small wash cloth under the cooling item, whether blue ice or a water bottle, to absorb any water that condenses on the outside.

Adult. Its funny, I was "thinking" about an insulated bag...well actually texted son yesterday he need an insulated lunch bag and this morning BEFORE this post that Articzone bag showed up on my facebook feed...weird huh!!

Beyond Elmer's suggestion wrapping it in paper then in toweling or heavy bedding will help keep it cool as long as he does not leave it where the sun hits it. You can suggest all kinds of things but it is better if he picks it out himself.

Buy the reusable gel ice packs to fit the dimensions of the cooler. I prefer the solid blue ice over the flexible ones. Put the pack on top of the food, not under or beside it. It's just like packing any larger cooler. If it's going to be a in a hot vehicle all day than use a few flat mini ice packs under the food for extra coldness.

Do remember those ice packs condense moisture from the air. Food and the area it is placed needs to be protected from the moisture.

"If it's going to be a in a hot vehicle all day....."

Lunch doesn't spend all day waiting to be eaten, especially not the lunch of a young man. Especially if it spends the night in the fridge (not in an insulated bag, that defeats the purpose of a night in the cooler), it will stay cool without too much worry until it's eaten.

Really Elmer? You nitpick this? Are you really that literal?

I know you spent your work life at a desk but plenty of workers do pack for the day. Mid morning snack, lunch, extra beverage, afternoon snack etc. That is why men and women often carry small cooler type lunch kits instead of the old brown paper bag. Work days are longer and so are commute times. He's not a child with a half sandwich, an apple and cookie to be eaten before lunch recess.

"Are you really that literal?"

Nope. But you're addressing a question that wasn't asked..

"I know you spent your work life at a desk"

Nope. But I didn't bring a lunch from home.

I have a big advantage over you - I was once a teenage boy and a young man. If he's going to school or otherwise has flexibility to eat when he's hungry, for most males in this situation, the food he brings will be in his stomach by noon, or no later than 1:00.

Clueless.

Sleep helps people who are cranky.

Maybe you should go to bed then..LOL

This might be overkill, or not. I just bought one of these for camping.

I don't park a car in the hot sun at a job site but if I did, I might use it.

https://www.amazon.com/gp/product/B07TJL6TBZ/

It's adjustable from -8F to 50F so it can be used to freeze or refrigerate.

I haven't received it yet so don't know how unwieldy it is, or how fast it runs a car battery down.

Look up "packit" on Amazon....they are freezable lunch bags and work great. When I was going to the office, I would pack my lunch in them and my food would stay cold at least until lunch and beyond (I would eat a yogurt around 3:00 and it would still be fine). When I get home I would put it back in the freezer and it would be ready for the next morning. They're just cloth lunch bags (they sell diff. sizes) with some sort of gel substance built in to the plastic liners. I have used these for years - used to also be able to get them at Staples or similar stores, not sure if you still can.

Cool product! (Pun not intended). Very useful.