October 1, 2015 I should brush right away after eating my favorite foods that are high in acid, like my breakfast grapefruit, soda, tomato sandwich or sour candies. TRICK. It’s true that acid causes tooth decay by breaking down tooth enamel. The trick here is that brushing right after eating acidic foods actually spreads it throughout the mouth, making the damage even worse. As your kids (or you!) enjoy sour candies this time of year, be extra cautious about when they or you brush. While it’s fine to simply rinse your mouth after eating acidic foods or candies, or drinking that soda, wait to brush for at least 30 minutes after consumption.