You can estimate the amount of fluid you need as a cyclist for a 60 minutes sweat test. Keep yourself hydrated during your ride, and weigh yourself nude. Now go out and ride your bike with the same intensity you do daily. Keep swinging for 60 minutes, and don't drink water during the ride. As soon as you reach home, absorb all your sweat in the towel and strip it away from your body. It's time to weigh yourself again; the difference between both weights in grams will tell you the total amount of fluid you lose in milliliters.