Sugar-sweetened beverage purchases and intake at event arenas with and without a portion size cap

•This real-world study examined sugar-sweetened beverage (SSB) and food purchases and consumption during basketball games at sporting arenas with and without a voluntary 16-ounce portion size cap.•A portion-size cap at an event arena was associated with customers’ purchasing and consuming fewer SSB oz.•This study provides some of the first real-world evidence that an SSB portion-size cap policy may decrease SSB ounces purchased and consumed.