As childhood obesity has emerged as a major chronic health condition, translating nutrition and physical activity evidence into effective strategies for change in real-world settings has become a top priority. Our study aims to identify actionable implementation factors that affect children's water consumption in the Out-of- School Nutrition and Physical Activity (OSNAP) initiative--a group-randomized trial designed to create nutrition and physical activity policies and practices that promote child health. In this chapter, we investigate the key implementation determinates of practices that promote water intake. National data suggest that children are not consuming enough water. Experimental evidence has linked increased water consumption to obesity prevention, and the National AfterSchool Association named serving water as one of its nutrition standards. Also, water access has been documented as an area of inequity in the city of Boston. Significant changes in water consumption were found in the main effects of the OSNAP trial. (author abstract)