I remember someone questioning Dacre Montgomery's acting choice of putting toilet paper on his tongue in this scene (if you mentioned this, tag your post).
LSD is liquid and is usually ingested on blotting papers, sometimes with art or designs.
Given this is a high school party, it's safe to assume that Tommy loaded up a couple rolls of toilet paper with various blots on random sheets and it was a luck of the draw sort of situation.
Final answer? Tommy's rager had a game of LSD spiked toilet paper. Lucky licking!
If anyone is interested about the scene in context, here's a video.
















