Eat a lot of asparagus and beetroot but don't drink a lot all day. Then piss in a frying pan and stick it in the freezer. Once it's frozen you'll have a disc of piss that you can throw through the letterbox of his house or any open windows when he's asleep. Then when he wakes up it will have melted and there will be a purple stain from the beetroot and an extreme odour from the asparagus.