You fart in a cup that used to contain pineapples and convince your friend that he shouldn't waste the juice and have him drink it.
Chris: *farts in cup and seals it with lid*
Tanner: Dan, don't waste your pineapple juice, drink it
Dan: Alright. *opens lid, drinks juice* UGH! it tastes like crap!
Chris: That's my special Pineapple Fart Cup