It is a myth, disconfirmed by numerous studies, that sugar consumption causes hyperactivity or other behavior problems in children or adults. This myth may be maintained by confirmation bias and social reinforcement. Conversely, numerous studies show that sugar consumption improves athletic, cognitive, and academic performance and may increase self-control and reduce aggressive behavior. These effects may be most apparent shortly after sugar has been consumed. While the brain utilizes large amounts of glucose, the exact physiological mechanisms responsible for the performance-enhancing effects of sugar consumption are still debated. Psychological research and theorizing on the effects of sugar consumption should avoid speculative explanations in terms of “mind” and “willpower,” and focus on observed behavioral effects. For behavior and academic problems, limiting sugar consumption should not be a treatment focus and may be counterproductive.