The document describes an experiment that studied how the kidneys regulate plasma volume, osmolality, and pH in response to consuming different beverages. Adult human subjects were assigned to drink either water, Gatorade, Coke, or nothing. They then voided and tested their urine every 30 minutes for 120 minutes. Urine volume, specific gravity, and pH were measured after each void to see how fluid intake affects urine composition. Subjects fasted for 5 hours prior to standardize their physiological state at the start of the experiment and only drank 8 ounces of water if needed.