Cool off with water, not sugar or alcohol. “Summer drinks can sabotage a weight-loss plan,” says Dena McDowell, M.S., R.D., a nutritional expert for the weight-management program TOPS Club, Inc. Besides sugary soda and high-calorie energy and sports drinks, liquor can also be a diet derailer. Says McDowell, “A 6 ounce margarita is about 300 calories, while wine coolers and beer yield anywhere from 100-150 calories per serving. It’s better to stay hydrated with plain water, or to have a white wine spritzer, which has fewer calories and less alcohol than a regular glass of wine.