

Metal, glass or ceramics are all fine as long as you fill them yourself with tap water. Bottled water from the store often contains microplastics that got in there during the filling process so the container material isn’t the only thing to consider.
My stepmother is in her mid 40s and does exactly the same thing. Also a disgusting looking blanket from her childhood that she even takes with her on holidays. I mean we do stir her up for it (sometimes she “wears” it to sleep like bandages covering her entire head which looks hilarious) but I’d say it’s weird in a wholesome way. Most people have some of those little quirks.