There are 3 main reasons that mainstream energy drinks have a bitter 'bite' to them. #1: Taurine is a most important additive that helps to potentiate the caffeine to reach the bloodstream faster, as well as speed up the metabolism for most people. However, Taurine is acidic, which in turn means it is also bitter/sour. Combined with citric acid, sodium citrate, vitamin c, tartrate, sorbic acid, benzoic acid, and the b-vitamins as well. Not all have the same exact ingredients, but they all contain a lot of acidic-bitter flavors. #2: The abnormally sour 'bite' actually stimulates the brain to release adrenaline and/or serotonin in most people, in the same way spicy foods do, generally. It's a cheap 'extra kick'. #3: Many people have a very mild 'addiction' to sour/sweet flavors. Like the candy, Sour Patch Kids, which is the most popular non-chocolate candy on the market, people have a strange enjoyment of the sour-sweet combination. Much like salty and sweet as well. They compliment each other. However, drink in moderation because they are very unhealthy unless you buy organic versions.