Why do your braces feel weird when you drink cold water?

Answer 1

Because the wire is made of metal, and when metal is warm it stretches out, but when its rapidly changed to a cold temperature, (from the cold water), the metal contracts and gets tighter, causing your braces to pull on your teeth a little bit.

Answer 2

Since there is more stuff in your mouth (and your mouth isn't used to it) , and because of food getting stuck in your braces (which can make the wire "tighter").