Never let a baby or small infant drink anything but milk or water from a bottle or a cup with a lid. Letting your small child drink juices, fizzy drinks or sweetened liquids from a lidded cup can lead to severe tooth decay.
When an infant’s teeth have frequent or prolonged exposure to liquids that contain sugar, like sweetened water and fruit, it can damage their teeth, particularly front teeth.
Tooth decay can occur when the baby is put to bed with a bottle containing sugary drinks, or when a bottle is used as a comforter for a fussy baby. The sugary liquids coat the teeth while the child sleeps or is being comforted.
Bacteria in the mouth use these sugars as food – producing acids that attack the teeth. Each time your child drinks these liquids, acids can attack for 20 minutes or longer. Continued use of sugary drinks in lidded cups leads to multiple attacks of acids and the teeth can decay.
If you really want to give your child sugary drinks, the safest way is with a straw, where the liquid passes the front teeth.