Caffeine Can Make You More Alert (From WebMD)

Info Source: http://www.webmd.com/add-adhd/slideshow-brain-foods-that-help-you-concentrate?ecd=soc_fb_011713-am_ss_brainfoodsconcentrate

There's no magic bullet to boost IQ or make you smarter -- but certain substances, like caffeine, can energize and help you focus and concentrate. Found in coffee, chocolate, energy drinks, and some medications, caffeine gives you that unmistakable wake-up buzz -- though the effects are short term. And more is often less: Overdo it on caffeine and it can make you jittery and uncomfortable.