Be toast
Definition 1 of 1
Pro Tip 1/3Serious Consequences
Implies that the speaker will face negative outcomes, often used humorously for minor issues. 
If I eat my sister’s chocolate, I’m toast when she finds out!
Pro Tip 2/3Informal Expression
Used in casual conversation, not suitable for formal or professional situations. 
He's toast if he doesn't finish his project by tomorrow.
Pro Tip 3/3Suggests Imminence
Conveys that the trouble or failure is about to happen very soon, almost a certainty. 
We're toast if that storm hits us before we reach shelter.