How can I pwn my friend for doing this?

I asked this before but one person answered and it wasn't what i was looking for. no offense person who answered my previous question. so a couple days ago my friend said turn around and i did. He spit phlegm on me. Know the worst part, when he spit I gasped and in that moment gasp when my mouth was open some flew in my mouth. I need to get him back, that was the most disgusting thing in my life. so what awesome prank can i play? keep in mined i can't do anything strength related like rip his mouth open and drop a bug in because he's stronger then me, as is everyone. I'm 13, 62 pounds, see. so what can i do to possible disgust him even more? please, don't say do it back again, I tried it already and he seen it coming.