Do you know what makes bath bombs fizzy? Well, Many bath bombs contain citric acid, as found in citrus fruits, and sodium bicarbonate, which is a weak base. The dry chemicals are stable, but in water, they react together to produce carbon dioxide bubbles (fizz) and, as a by-product, sodium citrate salt. Bath bombs have become an interesting way of bathing in recent years. Dive the bath bombs in the bathtub and they begin to release it is fantastic fragrance and rich bubbles, making your bath time more enjoyable.