“Quit playing with your food!”

You're eating dinner with your family. Your son doesn't like the vegetables, so he's doing things like picking them up and putting them down, making piles with them, and so on to avoid eating them. You say:

Quit playing with your food!

Quit (doing something)!

Tell people "Quit ___!" when you're annoyed and want them to stop.

"Quit" is a little more casual than "stop".

(someone) is playing with (their) food

When kids don't want to eat their food, they "play with" it. "Playing with" your food means touching it, moving it around, or doing other things instead of eating it.