For longer or more intense efforts of an hour or more, a sports drink containing electrolytes and sodium will be needed. We suggest aiming to drink at a rate of 10 to 12 ml per kilogram of body weight, about a 600ml bottle every hour for a 68kg rider.
The more you sweat, the more you are going to lose those salts and those minerals. If you find yourself tired, irritable, headaches, or other symptoms while cycling, then you may have insufficient water. Go Drink More Water!