Caffeine doesn't create energy; it simply masks fatigue by blocking adenosine receptors. After consuming caffeine, a backlog of adenosine can lead to increased sleepiness once its effects wear off. To maximize energy levels, it's beneficial to avoid caffeine for the first 90 to 120 minutes after waking, allowing adenosine to clear from the system naturally. Understanding this mechanism sheds light on our historical reliance on natural light cycles and the impact of artificial lighting on our energy management.