eat a bag - You say it when you’re mad at someone at work or school, and

You say it when you’re mad at someone at work or school, and you want them to feel the same pain you do.

My coworker said, 'Eat a bag!' when I took his coffee.

My friend said, 'Eat a bag!' when I took his lunch.

I said, 'Eat a bag!' when my boss gave me extra work.