When to Drink Your Bowel Prep The day before your colonoscopy: In a pitcher mix the 8.3 ounces of MiraLAX® with the 64 ounces of Gatorade®. Stir/shake the contents until the entire contents of MiraLAX® are completely dissolved. Chill if desired. Do NOT add ice, sugar or any other flavorings to the solution. Morning Appointments (Before 12 noon)