eating one's vegetables
Getting made to do something really nasty as a consequence for being a terrible kid. This could mean butt sex, eating cum, getting your hands up your backside, or getting peed on by a man in a golden helmet.
He had to eat his vegetables after he called his teacher a f***ing idiot in front of the whole class.
She got made to eat her vegetables because she insulted her teacher and called her a f***ing moron.
He had to eat his vegetables because he told his principal to go f*** himself.