Packs of these recently showed up at a Dollar Tree near me. I looked at the ingredient list and realized that they are water-based. I actually did try out the polish, and they're really bad. I hope no one ever makes the mistake of starting their foray into the world of nail polish with these! Anyway, I emptied them out (mostly in the trash, just in case), washed them with soap and water, let them dry completely, and now have bottles for my franken creations.
Edited to add: Since the original polish in these bottles doesn't pour out easily, I inserted a drinking straw and blew into the bottles to push most of the polish out (did this in a bowl to contain splatter). Then it was pretty easy to finish up rinsing with water (still with straw as it helps to force air into the bottle)
Now if I could just find an easier way to get those stickers off... The first one was a pain. They're the perfect size though!