An annoying know-it-all. Someone who thinks they have all the answers, but really they don't. Snapple cunts are useless.
The origin of 'snapple' comes from the useless snapple facts (the little facts on the back of snapple-drink lids)
Conor: Please pick on me, I know the correct answer to the question!
Teacher: Shut up, you're such a snapple cunt.