Replying to Revenge prank?

So me and one of my dads friends are in a war. It started with small pranks that are an inconvenience, if anything. So the last one was a pit farther. While he was at my house. He switched my shampoo for watered down maple syrup. I was almost out anyways, and I shower in the morning, so I figured I was out and my mom replaced it and I am too groggy in the morning to realize something was wrong. So I used that for 5+ days during the summer, until his daughter told menthe next week. So I need a good way to get him back. He lives too far away to go there just for that, so I need something to do if he is at my house/I am at his house. Oh and I recommend the syrup prank to anybody who needs a good one. +k for the best answer