LOL. I didn't get the title for a second, I thought you just meant plastic shoes. LOL. Its been a long day XD
I've used a plastic container to hold a betta for a few days once. I know some members use them long term, and I haven't heard any complaints about them. The only thing I felt bad about them, was that some aren't completely transparent. I had a betta in one that had a bit of a murky view, because of the plastic that was used. My lil' guy didn't like not being able to see out of it clearly. So if you use one, make sure the betta can see clearly out of it.
I've actually heard some really great things about using plastic containers. Good luck!