Water is an essential nutrient with multiple significant role in the human body. The need for water intake is even more pronounced during prolonged aerobic activities. Numerous studies confirm that dehydration reduces work capacity, leads to premature fatigue and fatigue of the nervous system. This work will be based on the guidelines given by the American College of Sports Medicine and review articles related to the topic of hydration. Aerobic sports activities are generally considered submaximal activities of longer duration. Such activities rely mainly on aerobic metabolism and on work of large muscle groups. The aim of this work is to show the recent findings and recommendations related to the hydration of athletes before, during and after the competition, in particular for sports like marathon, cycling, triathlon and outdoor swimming. Sports drinks play an important role in professional sport and optimization of sports performance particularly in activities of long duration. Sports drinks are well recognized by athletes as an important factor in their success, therefore, guidelines will be presented in this regard. There is great variability among individuals in factors affecting individual fluid needs. For every athlete is necessary to determine individual nutritional needs and needs for fluid intake with respect to activity and other impacting factors in certain segments of the training cycle and competition. Long-term activities are linked to some health problems which will also be presented in this work.