When I drink a bit it seems my sleep is better than usual. But the few times I've gotten really drunk, the type that leaves you with a bad nauseous hangover in the morning that lasts for hours, my sleep has been terrible. My dreams are shallow and mundane and repetetive, and seem to express the nausea I'm feeling, making me more nauseous. I'll wake up in the middle of the night with a hangover and realize I had just been dreaming obsessively about trying to work out some nonsensical math problem or something. I experience something similar when I fall asleep while sick or after actually working on something repetetive and mundane all day.