Nudges offer a promising tool to reduce sugary drink intake among children who are most at risk for diet-related disease. The objective of this study was to examine the impact of online store nudges on purchases of sugary drinks for children in lower-income households. Caregivers with lower-income were recruited to an online shopping experiment and instructed to spend $10-$30 on three beverages for their child aged 1-5 years. Participants were randomized to navigate an online supermarket in its standard version (n = 1106) or a version with nudges (n = 1135), including a product placement nudge (i.e. placing healthy beverages in prominent positions) and a swap nudge (i.e. offering a swap of water, plain milk and/or 100% fruit juice upon selection of sugary drinks). On average, participants purchased 1887 (SD = 2113) and 620 (SD = 1528) calories from sugary drinks per basket in the control and experimental conditions, respectively. Model-based results indicate that those in the experimental condition purchased 1267 (95% CI: 1419, 1114) fewer calories from sugary drinks, and fewer grams of total sugar (β = -253.5 g (95% CI: -286.3, -220.6)) and added sugar (β = -287.8 g (95% CI: -323.1, -252.5)) purchased from sugary drinks. In conclusion, nudges may be an effective, acceptable, scalable strategy for leading caregivers in lower-income households to purchase fewer sugary drinks for their children.