i start by waking up at my regular time, working all day, eating dinner, then hitting the road around 7pm. i chug a large bottle of mocha Frappucino (starbucks brand) while the gas tank is filling right at the start of the drive. after that, i maintain the buzz with diet pepsi, 20 oz per tank of fuel -- at my speed, that's about 4 hours. i also drink water along the way, and i pee in a 32 oz gatorade bottle, which can be dumped at fuel stops or just poured out the window going down the road. the wide mouth bottle is key, as is cruise control.
i listen to rollins spoken word, which is kinda like audiobooks i guess. and whatever other favorites are on my ipod.
following that formula, i've made it solo from Charlotte to Detroit (11 hours), Detroit to Atlanta (12 hours), and Detroit to Gainesville (18 hours).
i eat high-protein snacks like beef jerky and almonds. avoid sugar, as it'll kick up your insulin and make you sleepy after the initial buzz.