As a stimulant, caffeine can definitely increase your energy level. Did you know it can decrease it, too? It all depends on how sensitive you are to caffeine, and when and how much you consume.
Caffeine does help increase alertness, so having a cup of coffee before going to a meeting or starting on a project can help sharpen your mind. What about energy drinks? While increasingly popular, there's really no magic formula here. What gives these drinks their jolt is good old-fashioned caffeine. Caffeine content varies widely among energy drinks. Many contain as much or more caffeine as a cup of coffee, along with loads of sugar.
But to get the energizing effects of caffeine, you have to use it judiciously. It can cause insomnia, especially when consumed in large amounts or after 2 p.m. (or noon if you're caffeine sensitive). Some people are so sensitive to the effects of caffeine that having a single cup of coffee in the morning can interfere with their sleep at night. And that can definitely lower your energy. If you're such a person, it's best to avoid caffeine entirely.
For more advice on ways to feel energized, read Boosting Your Energy from Harvard Medical School.