Another way to do this is to leave an inch when cutting offf the top. That makes a hinge. I poke a hole on the bottom just below the cut and on the top just above the cut. through this I put a twistie tie. Keeps it shut when it's cold and before seeds germnate (keeps things moist) then just untwistie tie and open it up with the hinge. Can use them year after year.

I bought a cheapy sodering tool to use when making bottom holes and the holes for the twistie ties. Do this outside so you don't breath the chemicals.

You can also use them to make slug traps. Take the top part off right where it starts to narrow. Then flip it around and insert it back into the bottle. Staple or duct tape the two together. Fill the inside with slug bait. Put in your garden and the slugs will crawl in there and not be able to get out.

I haven't made one myself yet, but heard it works from others.

The slug trap should also work well for a minnow trap. Drill a few 1/16" holes to let water in, then bait with bread or crackers. You might want to add rocks to weight it down, and add a string so it doesn't float away.

Making them the same way Faltered said into slug baits, you can also use them for wasp traps. I bought a wasp trap that was basically the same thing & am now making my own (because I have plenty of wasps! LOL!). You put something like beer or apple juice or sugar water in the trap. The directions on my trap said to stick something like raw hamburger meat or tuna fish or cat food in the holes but not enough to stop up the hole.