Incidentally, I'm pulling a double shift today. I took the precaution of preparing myself 500+ mL of sweetened espresso with chocolate in a flask. (Well, more of a bottle than a proper flask, but it's the idea that counts. I wonder if any of the Junque Shoppes will sell a replica of Mad-Eye Moody's flask? That's some cool equipment there.)
The plan is to not hit the coffee unless and until I actually start feeling groggy, though I may violate that straight off because it's so tasty-smelling.