Don't know about other kids, but mine love to try to take lids off things. Usually things that I don't want them to touch. And often it goes badly because they are not very skilled at actually undoing things yet.
So I figured that I'd channel their inquisitive energy into actually undoing things they were allowed to and thus making them more skilled at undoing things while teaching them there are things they are allowed to undo, and things they aren't.
Step One: collect various bottles with different types of caps. The ones I collected were mostly screw on, but a few had other features as well. One had a pump top (shampoo bottle), and a few had snaps.
Step Two: wash said bottles and cut the tops off. I let them sit on the bench for a few weeks as well, but that's not really necessary. That was more disorganisation.
Step Three: glue the bottles onto whatever you have handy. Ideally I would have used some wood, but I didn't really have any handy, but I did have cardboard which works just as well. Possibly better, because it's light enough for the kids to carry around too. I just used a hot glue gun and it worked fine.
Step Four: show the kids how to use it. Seriously, that's pretty much it.
I a little bit wish I'd covered the cardboard with some pretty paper or fabric first, just to make it more visually appealing, but it doesn't really matter. The kids love it. Rachel takes all the lids off and puts them into the red container to hide them, but they always come back out.
Just so you know, I used the following bottles: milk, juice, mayonnaise, soy sauce, food colouring, shampoo, soap, another soap, stock, water and a powder bottle. The powder bottle lid doesn't come off, it just turns.
There you go. A perfectly good way to reuse bottles and entertain kids at the same time.