eat a bag
You say it when you don’t like someone or something, and you just want them to vanish, or at least swallow a bag of gross stuff.
My teacher said, 'Eat a bag!' when I told her I was going to fail the class.
My mom said, 'Eat a bag!' when I told her I was moving out.
I said, 'Eat a bag!' when my crush asked me out and I was mad.