Energy drinks contain caffeine as a key ingredient. Some people are sensitive to caffeine and when consuming caffeine-containing products, they may become restless or even get insomnia.

In its scientific opinion on the safety of caffeine from 2015, the European Food Safety Authority (EFSA) states that caffeine doses of about 1.5 mg/kg body weight may increase sleep latency and reduce sleep duration in some individuals, particularly when consumed close to bedtime. Energy drinks contain about the same amount of caffeine as a cup of home-brewed filter coffee. Furthermore, the caffeine content of energy drinks is declared on the label, so consumers can make an informed choice. In general people sensitive to caffeine should choose not to consumer energy drinks.