You probably remember the homemade volcano experiment from grade school, when we mixed baking soda with vinegar to create an eruption. That's the same concept as what's happening inside our baked goods, but there are a number of different acids that can be used to activate baking soda besides vinegar. Common acidic ingredients used in baking are buttermilk, sour cream, brown sugar, lemon or orange juice, yogurt, molasses, cocoa powder (natural unsweetened not Dutch process), and honey.