You will perspire more heavily than normal while bicycling. Dehydration, or loss of body fluid, is a serious condition and should be avoided. Try to consume more water than normal the day before your ride. This will super-hydrate your body in preparation for the ride.
During your ride, drink the equivalent of one water bottle (20 oz.) in small amounts each hour or every 12 to 14 miles.
Electrolyte (sport) drinks can greatly improve your riding enjoyment. If the weather is exceptionally hot and humid, increase the amount you drink and drink more often, alternating water and sports drinks.
Many cyclists have found benefit from an electrolyte replenishing tablet called Nuun. It can be found at many bike shops and on-line. One tablet per water bottle has helped cyclists from getting leg cramps after the ride.
If you find yourself feeling lightheaded and ill on a very hot day, if you have ridden for a couple of hours and have not urinated, or if your skin feels cold and you get goose bumps, you may be experiencing dehydration. Get off your bike in some shade and re-hydrate before continuing your ride. The best option for an enjoyable ride is to eat and drink at a slow, steady pace. Plan when and what you will consume and you will find that your muscles will enjoy the ride as much as you will.