Energy products such as “Red Bull” “Monster” and “Rock Star” can contain very high levels of caffeine or other stimulants (usually guarana or ginseng) that can cause adverse (negative) health consequence including dehydration. A soda such as Coke contains 34 milligrams of caffeine, while energy products can contain anywhere from 75 to 200 milligrams. Hence, they are very powerful and need to be used with caution. Large doses of caffeine, especially in younger bodies, can boost heart rate, raise blood pressure and dehydrate the body.  Like all stimulants—that’s what energy drinks are!—they can also keep you from proper sleep, already a problem for most teens.

Energy drinks become especially dangerous when they are combined with alcohol or other drugs. For example, when mixed with alcohol, which is a depressant, energy drinks can mask the effects of the alcohol.  Therefore, a person may not realize how drunk he/she is and then will often underestimate his/her level of intoxication. This means he/she will either keep drinking (very dangerous) or choose to do something he/she shouldn’t (like drive a car).

In addition, both alcohol and energy drinks are dehydrating. If a person survives the dangers above, he/she will suffer a more intense hangover the next day.

(Source: https://www.brown.edu/campus-life/health/services/promotion/alcohol-other-drugs-other-drugs/energy-drinks)