Babies under ten days, omg. They certainly cannot consume foods other than breast milk. All they need is a little milk.
If the mother is not able to produce milk, like in rare instances, the babies are given formula milk but only if the doctor recommends it, like lactogen. Grandmas also give warm water with a little sugar but that is not recommended by doctors.
If there are other new mothers around, milk can be requested for the baby if the baby's mother is totally unable to produce milk.
Another thing to note is that the mother can give milk even if she has only a little milk because, the more you give, the more it will be produced.
A certain bonding should be formed between the mother and baby and for this, others should help the new mother completely. A mother who has just delivered will be in no condition to move around like normal, so others should help her definitely and make sure that both she and the baby feel comfortable while feeding.
The new mother will be accustomed by the time a month is over.
If milk is not enough, remember to ask the doctor for medicines. Certain Ayurveda medicines like shatavari help in producing more milk.
Care should also be taken by the mother to keep her breasts clean always otherwise there is a chance of infection and fever which can also affect the child too.
From six months onward, the baby can be given fruit juice, porridge, mashed fruits and so on.