I personally prefer to stay away from products like that because most aren't FDA approved (examples: hydroxycut, Xenadrine, etc).
Depending on your circadian rhythms, it's quite common to get an afternoon lull around that time. Probably the best thing to do is to get up and get moving - if you work and can take a trip through the office (up/down stairs), etc. Increasing your heart rate will help and is likely the safest. Caffeine doesn't have much of an impact on me, so having a coke doesn't do me much good one way or the other.
The active ingredient in 5 hour energy is caffeine (comparable to a good, strong cup of coffee).
Carbs become energy as well, so you can always have something sugary, too to combat your lull. A trick we used to use in gymnastics was to eat pixie sticks, suck down powdered Jell-O, etc. before going out for a routine, but the chances of crashing and burning later go up dramatically, too.