Energy drinks got their start in Japan where executives wanted an extra boost to get ahead. Today, the often intensely caffeinated beverages are doing brisk sales in many parts of the world. Here’s a look at what was (and is) in those energy drinks, and some perspective on their impact: From researcher Kathleen E. Miller: “I’ve found that if you report that you have six or more energy drinks over the course of a month, you’re also more likely to report that you got in a fight last year, that you had sex without a condom or that you drove without a seat belt.” Of course, that could just be because you’re awake more.