Answer:
I come with a train and go with a train and the train doesn't need me but can't go without me.
Break me and I am better immediately set and harder to be broken again.
I am the kind of soda you must not drink. What am I?
The more I dry, the wetter I get. What am I?
I have no voice but I can teach you all there is to know. I have spines and hinges but I am not a door. Once I’ve told you all I cannot tell you more.
What is yours but only used by others?