Sweating like a fat bird, in a bin bag, at a barn dance

When a person sweats profusely due to the overexertion of a physical activity.

Dan : "Hey Abbie, how's the workout going?"
Abbie : "Yeah, really great thanks. I'm sweating like a fat bird, in a bin bag, at a barn dance!"
Dan : "Good work, you won't be a fat fucker for much longer!"