The correct phrasing is "Can energy drinks kill people?" and the answer is yes, especially if they are mixed with alcohol. There have been several cases of people having a stroke by mixing an energy drink with liquor.
5-Hour Energy and some others provide 'energy' through B complex vitamins. Some of these can be toxic at high levels. B1 can damage your heart, B6 can cause long term nerve damage and B9 can severely damage your kidneys. Remember you get B vitamins from food as well as high doses from energy drinks. Some of these can build up over time and cause serious damage or death.
ill tell you a story...one of my good friends,matt yuhas from east moriches out on long island was challenged to do a "four loko challange". its 4 four loko's in one hour, he completed it. went to sleep and never woke up, died at 18 years old. anything can happen because different people have different medical problems.
In certain companies, people make a really good energy drink, but the prices to make it go up, so the company gets cheap chemicals to replace it. On your heart, the cheap energy drink is like a ticking time bomb, waiting to go off. The chemicals can do some really bad damage to your body, and then the bomb goes off. I'm not sure which company makes their energy drinks like this, but always look at the food labels.