A person can only stay alive a few days without water, or liquid of some sort.
Water is lost several ways.
Just by breathing, urinating and sweating, a person can loose up to 12 cups of water every day. And this increases with intensity of exercise. It is so important to replenish this liquid by drinking water all through the day. The benefits include better body functioning, a clearer head, less headaches, decrease in mood fluctuations, weight control and increased physical performance when doing the things we love, such as cycling. It is best to drink 1 to 2 cups of fluid before exercise and then drink often during exercise as well as when you stop exercise.