this is what i found out.. hope its useful
How much juice, milk or water should I give my baby each day in his sippy cup?
In your 'sippy cup', you'll want to keep it exclusively for certain kinds of liquids. Remember that juice, milk, and water are to be used in small amounts during your baby's first year of life. After the first year of life, you can give up to four ounces at a time in a baby's 'sippy cup'. It's a very small amount, and it's your baby's total juice intake for the entire day. You may fill it up with additional water, but that's it for apple juice in a day. Some people would be surprised that this tiny little 'sippy cup' contains actually about ten ounces' worth of fluid. This would be almost your baby's entire milk intake for one day; in fact, two of these 'sippy cups' is your baby's full milk intake for one day. So remember that 'sippy cup' sizes are very deceptive. Give small amounts. Let your baby only carry water around with him in a 'sippy cup' and not juice or milk.