u/IRNotMonkeyIRMan

So I have a weird idea. I have a few vacuum flask water bottles that have lost their vacuum, and I don't want to just throw them away. Has anyone here though about or tried to drill a small hole in the bottom and fill it with spray foam (the kind that fills without expanding a lot, window and door kind) and then capping the hole? I thought I might try on one I don't care too much about just to see if it works.