BOYS ONLY HELP ME OUT! WHY DID HE DO THIS? EHHHHAYY.?

today my friend was being stupid and threw my water bottle near to dan this boy< and he new it was mine and he then picked it up and pretended to pee out of it like put it down near his penis and was tipping water out .. then he threw it down hardly on the floor then looked at me then carried on with what he was doing.. why do you think he did this?