The Caffiene Nap:

The Caffeine Nap is simple.  You drink a cup of coffee and immediately take a 15 minute nap.  Researchers found coffee helps clear your system of adenosine, a chemical which makes you sleepy.  So in testing, the combination of a cup of coffee with an immediate nap chaser provided the most alertness for the longest period of time.  The recommendation was to nap only 15 minutes, no more or less and you must sleep immediately after the coffee.