Most energy drinks have high levels of caffeine, sugar and herbal supplements, such as taurine. Many contain such large amounts of these substances that they can cause irregular heartbeat, irritability, nervousness, nausea and sleep problems.
If consumed when you are dehydrated, with alcohol, or too quickly before a sporting event, these drinks can be dangerous. Fainting or even a heart attack could occur, say doctors at the Mayo Clinic. Remember, energy doesn’t come in a can!