Why do energy drinks make me tired? The crash mechanics and the best cutoff before bed
Dr. Susan Carter, MD: Endocrinologist & Longevity Expert
Nov 21, 2025 · 14 min read
Energy drinks can make you tired because caffeine and sugar can create a short-lived spike followed by a “crash,” and caffeine can also disrupt sleep long after the can is empty. If you keep asking “why do energy drinks make me sleepy,” the answer is often a mix of brain chemistry, blood sugar swings, hydration, ...