I used to use plastic but they do stain easily and then I found out that plastic can cause contact dermatitis. I went to a stainless steel water bowl and didn't like how part of it wasn't getting clean. Then I went to ceramic which I love but Ellie's bowls developed this strange smell. We bleached them but the smell won't totally go away. So now those are out.
Now I use Pyrex because they are made in the US and because I don't want Ellie around glass unsupervised, she will be getting Rubbermade for her cage.