On average, you should take a rehydration break at least every 20 minutes. Most people would stay adequately hydrated by drinking about 7 to 10 ounces of fluid every 10 to 20 minutes during exercise. But your exact need depends on things like how hard you're working, whether you are indoors or outdoors, and your age, gender, and weight.

It's also helpful to drink two cups of fluids (about 17 to 20 ounces) about two to three hours before a workout.