I once asked for a water cup at mcdonald's and then I filled it up with soda without the employees knowing
Why would you fill it up with anything besides water?
I was being a jerk and I wanted to be a bully.
So you basically stole from them since you got pop with out paying for it. I think that that is wrong.
I already know I was a jerk and won't ever do it again.
You learned from your own mistake, that is a good thing. I am happy to know this about you, realizing you can get into trouble is probably what drove you to stop doing things like that. I can trust you more now than ever before!