Bart: And, for the college bound... pep pills!
Lisa: (reading the label) "Trucker's Choice!" Thanks, Bart!
--The Simpsons ..... duh.....
Any number of stimulants that are marketed towards truckers and other long distance drivers, and are available at any number of truck stops or convenience stores. Including, but not limited to, ginko biloba, ginseng, mini-thins or any other ephedrine, and caffeine pills (such as No-Doz). They usually taste like chalk and are never the healthiest of options.
The most interesting, effective, and tasty kind I've encountered was a mocha flavoured (although it tasted more like chocolate) ginseng syrup mixture. It even made driving across Kansas at night quick and enjoyable.