The best drinks for childrens teeth are milk or water.
If you do give other drinks then use a straw to help direct the drink away from teeth and minimise damage.
Natural fruit juices or squashes still contain high levels of fruit acids. Even drinks marked no added sugar still contain sugars that can form acids and cause tooth erosion.
Always dilute squashes correctly. You can also dilute natural fruit juices with water to reduce the risk of tooth damage.
Encourage your child to take drinks over a short time, rather than constantly sipping as this reduces the time in contact with the teeth.