Example: Rob:"Lemme get a triple stacker and a large soda"
Girl:ya total is 3.50
Rob:"Chu gon throw some fries on dat ma?"
Girl:(sneaks fries into bag)
Rob:"iight i fucks!"
This would be used in a situation where an individual with a good behind is walking in front of you, "shaking" their ass. By asking if they want fries with that, you're asking if they want to have intercourse, where the fry is meant to simbolize a dick.