Performance enhancer: coffee.

http://www.webmd.com/diet/slideshow-energy-mood-boost-diet?ecd=wnl_alt_061111

Coffee
Coffee may be one of the world’s most popular pick-me-ups, and evidence suggests it works – at least in the short-term. Caffeine steps up the body’s metabolism, temporarily improving mental focus and energy. Frequent mini-servings will keep you alert and focused longer than a single large dose. Just beware of drinking so much coffee that you can’t sleep at night. Lack of sleep is an obvious energy-buster.

Joe DiMaggio supposedly had the clubhouse guy bring him multiple half cups of coffee during games.  I always considered this his greenie, the amphetamine of the 1930s-1940s.

http://en.wikipedia.org/wiki/Amphetamine

During World War II amphetamine was extensively used to combat fatigue and increase alertness in soldiers. After decades of reported abuse, the FDA banned Benzedrine inhalers, and limited amphetamine to prescription use in 1965, but non-medical use remained common. Amphetamine became a schedule II drug under the Controlled Substances Act in 1971.