Despite what you see in the supermarket, fruit juice is not necessary for babies or toddlers.
Fruit juice, even when it's labeled for babies and toddlers, is often full of added sugar. Even 100 percent fruit juice has a high natural sugar content. Sugar, even natural sugar, coats a child’s teeth, increasing his or her risk of dental cavities. In addition, because juice is so sweet, children will soon learn to prefer that over other more healthy liquids, such as milk or water.
Whenever possible, offer children real, whole fruits instead of juice. Whole fruit is full of fiber and vitamins that most juice is lacking. If you are going to serve juice, think of it as a dessert and give no more than 4 ounces a day to your toddler. Brush his or her teeth as soon as possible after.
Never put fruit juice in a bottle, because it increases the risk of cavities considerably, and never give fruit juice as a treatment for diarrhea because it will worsen the problem.