RE: How old should you be to drink G Fuel?

Here is the label available on line at G FUEL Ingredients & Nutrition Facts. I will comment only on the caffeine content and not on any of the other ingredients.

ie one “serving” gives you 150 milligrams of caffeine.

Next we have recommendations about daily caffeine limits for various age populations from Caffeine - Wikipedia

So, a full grown adult would max out on caffeine with just three doses (“servings”) of G Fuel. But note that a 12 year old child would get about twice the recommended daily max of caffeine with just one dose of this stuff. Give a kid a full serving of G Fuel and my bet is you would probably have to peel that kid off the ceiling.

According to the formula for adolescents above, ie 2.5 mg caffeine / kg body weight, that means your teen should weigh in at at least 150 / 2.5 = 60 kilograms or about 132 pounds / 60 kilograms before he/she gets ONE full serving per day.