Eva Longoria's trainer, Patrick Murphy, told PEOPLE that the actress guzzles "at least three liters per day" to maintain muscle tone and rid her body of toxins. So how much should you drink? "Half your body weight in ounces each day," recommends nutritionist Sophie Pachella, who founded the nutrition and fitness company EatStrong. "So if you weigh 120 lbs., drink 60 ounces or about 8 cups." Find water too boring? Add slices of lemon, orange, strawberry or cucumber to make it more flavorful.