Juices are popular among children of different ages. They are convenient and come in bright packages. But this is where the advantages of packaged juice ends. A glass of juice contains 5-6 teaspoons of sugar. The dissolved sugar immediately gets absorbed into the bloodstream which is bad for the metabolism of carbohydrates.
The American Academy of Pediatrics recommends eating fruit instead of drinking juice. Thanks to the fiber in fruit, the juice is absorbed gradually. You could also try to get them to drink fresh squeezed juice or a smoothie.