Caffeine tablets are one of the cheapest ways to get quick energy. If you are pretty short on money these are probably the way to go. Basically $12 for 100 caffeine tablets of 200mg. That is really pretty incredible. I always take them before my afternoon workout in addition to a scoop of NO-Shotgun.
Most people drink tons of caffeine throughout the day but, if you are more interested in performance- be sure to just load up on caffeine tablets pre-workout for a boost. That has a greater effect then slowly sipping on caffeine throughout the day.