Sodas and juice drinks are the real monsters when it comes to weight gain. A small soda is OK once in a while. But it's no substitute for healthier drinks. Sports drinks and juice drinks should be limited, too. These can contain almost as much sugar as soda. One cup of 100% fruit juice each day is fine—but that's all your teen needs. The rest of the time, water, low-fat or nonfat milk, and fortified soy milk are best. Note: If the kids drink milk, but adults get soda, this sends a mixed message.