Campaigns to improve beverage consumption typically focus on discouraging unhealthy beverages (e.g., soda), encouraging healthy beverages (e.g., water), or both. It remains unclear which of these strategies is most effective. We recruited a national convenience sample of U.S. parents of children ages 2-12 (n = 1078, 48% Latino[a]) to complete an online survey in 2019. We randomly assigned participants to view: 1) a control message, 2) a soda discouragement message, 3) a water encouragement message, or 4) both soda discouragement and water encouragement messages shown side-by-side in random arrangement. Intervention messages mimicked New York City's "Pouring on the Pounds" campaign. Participants rated messages on perceived effectiveness for discouraging soda consumption and encouraging water consumption (1-5 response scales) and reported feelings and intentions about drinking soda and water (1-7 scales). Compared to those with no exposure, participants who viewed the soda discouragement message reported higher perceived discouragement from drinking soda (Average Differential Effect [ADE] = 1.18), more negative feelings toward drinking soda (ADE = 0.83) and stronger intentions to avoid drinking soda (ADE = 0.45) (ps < 0.001). The soda discouragement message also exerted beneficial effects on perceived effectiveness, feelings, and intentions related to water consumption (ADEs = 0.33-0.68; ps < 0.001). Exposure to the water encouragement message had beneficial effects on outcomes related to water consumption (ADEs = 0.28-0.81, ps < 0.001), but limited impact on outcomes related to soda consumption. Across outcomes, results indicated diminishing returns from exposure to both message types. Messaging campaigns discouraging unhealthy beverages may be more promising for improving beverage consumption than messages only promoting healthier beverages.