A "sink snack" is a mixture of organic waste left in a kitchen sink after doing the dishes. S-Tier sink-snack if you cannot identify the origin of the leftovers.
Sink my shit
A game played by 2 or more people, each person takes a huge shit in the same toilet without flushing or wiping so that that it's just shit and no paper and when you flush, the toilet just fills up creating a massive floater or 'bung' thus sinking my shit and rendering the toilet useless.
Sam-"Yo man, you wanna play sink my shit?"
Jim-"Yes man"
When a girl (most likely an underaged teenage girl on a social networking site) takes a picture in the bathroom mirror, with her back to the mirror, and her butt seated on the sink, amplifying the rotundness of her butt. Often used to deceive potential men who would pursue sexual relations with her.
David: Broo! did you see that picture Kayla put up as her profile? I never noticed her ass looked that big before!
Brian: dude, it's not.. it's a classic case of sink booty.