Prove that there can't be evidence for a god or other supernatural things.

At first some definitions:
natural - as found in nature. And with that describable in that.
supernatural - not describable in nature; the opposite of natural.
evidence - a fact or information that is described in a structured way.

Prove by contradiction:
1: Let's assume there is evidence for something supernatural.
2: From (1) it follows that it has to be describable for it to be evidence.
3: If it's describable, it has to be natural.
(3) is a contradiction to (1) thus the assumption is false.
Thus there can't be evidence for something supernatural.