How can I get my friend back for this?

I was hanging out with him today and he said turn around so i did and he spit phlegm on me. some landed in my mouth when i gasped as the phlegm flew toward me. most disgusting thing in my life.Yes, I know my phlegm has been in my mouth before and iwas fine with it but someone elses? that's disgusting. I need a really easy and awesome prank i can play on him that's not bad enough s he will get hurt badly, but bad enough so he will suffer from what i went through. Keep in mind he's WAY stronger then me(everyone is, read my profile to find out my weight) so i need someting where strength won't be an issue, as i know some things with jokes are, as that one where you grabd his head and yank his jaw open and drop a worm or bug in his mouth.