I’ve seen people set up a system that bleeds a small amount of hot water into the line that fills the toilet tank to keep it up to room temperature or thereabouts. The idea is to prevent condensation on the outside of the tank.
They do that sometimes on Cape Cod. They run a hot water line to the toilet because it's so humid in the Summer time that the toilet tank constantly sweats and rots the subfloor. If you run hot water to it,this won't happen.
If you're getting hot water in your toilet and it's not supposed to be there, I'd call a plumber.
