Hydration levels significantly affect cognitive function, as the brain is largely comprised of water. Dehydration can lead to fatigue, reduced focus, and impaired short-term memory. Even mild dehydration can compromise cognitive performance and lead to errors in tasks that require concentration. Maintaining adequate hydration supports optimal brain function, enhances mood, and improves reaction times. Therefore, consuming sufficient fluids throughout the day is vital for supporting mental clarity and overall cognitive health, particularly during strenuous physical activities or hot weather.