My coworker and I dislike each other so much. I find the smallest ways I can be petty.
Can you name something you have done before?
I spilled water on his desk for no reason.
You don't have to like everyone you work with, buy you should try to keep your work relationships professional. Petty actions don't help anything and could lead to yourself losing your job.
When he gets mad, I do stuff more often.
That isn't very nice of you. It is wrong to be petty and to take things out on others. It's understandable to dislike someone but you shouldn't do mean things to them.