Acidic foods and foods that are high in sugar can be very harmful for teeth. Examples of these foods include sweets, chocolate, fruit juice with added sugar, fizzy drinks, cakes, raisins and biscuits. Acidic, sugary foods momentarily deteriorate the protective enamel exterior of the teeth, which make the teeth susceptible to decay and erosion. If you do give your child a sugary treat, make sure they have it with a meal and try to encourage them to eat cheese or drink milk or water to neutralise the acid in the mouth.