It is important for the child to eat a balanced diet, so some carbohydrates and starches are necessary. Starch-rich foods generally include pretzels, chips, and peanut butter and jelly sandwiches. Since starches and carbohydrates break down to form sugar, it is best that they are eaten as part of a meal (when saliva production is higher), than as a standalone snack. Provide plenty of water at mealtimes (rather than soda) to help the child rinse sugary food particles off the teeth.
As a final dietary note, avoid feeding your child sticky foods if possible. It is incredibly difficult to remove stickiness from the teeth – especially in younger children who tend not to be as patient during brushing.