The average person sweats an average of 0.5 liters/hour while simply walking around, going about his (or her) merry way.
Add strenuous exercise on a hot summer day, a person sweats about 1.5 liters/hour.
If we bike 90 miles/day at an average speed of 15 miles/hour, this means we can plan to sweat 9 liters/day.
Over the course of a 2000 mile trip, that's roughly 200 liters of sweat!