Restorative properties were shown by a combination of caffeine and the sugar glucose in an energy drink, and some degree of synergy between the cognition-modulating effects of glucose and caffeine was also suggested. In one experiment, a glucose-based energy drink (containing caffeine, taurine and glucuronolactone) was given to eleven tired participants being tested in a driving simulator. Lane drifting and reaction times were measured for two hours post-treatment and showed significant improvement.

A variety of physiological and psychological effects have been attributed to energy drinks and their ingredients. Two studies reported significant improvements in mental and cognitive performances as well as increased subjective alertness. Excess consumption of energy drinks may induce mild to moderate euphoria primarily caused by stimulant properties of caffeine and may also induce agitation, anxiety, irritability and insomnia. During repeated cycling tests in young healthy adults an energy drink significantly increased upper body muscle endurance. It has been suggested that reversal of caffeine withdrawal is a major component of the effects of caffeine on mood and performance.