Option 1: Water is not considered the ideal food for newborn babies as it does not provide the necessary nutrients and calories for their growth and development.

Option 2: Sugar is not a suitable food for newborn babies as it does not provide any nutritional value and can be harmful if consumed in excess.

Option 3: Honey is not recommended for newborn babies as it can contain bacteria that can cause botulism, a serious illness in infants. It is advised to wait until the baby is at least one year old before introducing honey.

Option 4: Milk is indeed the ideal food for newborn babies. It provides all the necessary nutrients, including proteins, fats, carbohydrates, vitamins, and minerals, that are essential for their growth and development. Breast milk is especially recommended as it also contains antibodies that help protect the baby from infections. If breastfeeding is not possible, infant formula is a suitable alternative.

Therefore, the correct answer is 4.