Even though this has been beaten to death already...
Pretty much all the same nutrients every person needs and gets through eating food that babies can't. It is not that they need something specific that you don't, it is that their bodies cannot process solid food and they cannot tolerate nutrient or electrolyte imbalances like you can.
As an example, infants can't drink cow's milk because it contains proteins, vitamins, and minerals in the wrong balance. Their kidneys can't haven't all of the proteins and minerals in the milk, but it also lacks the necessary amounts of vitamin C and iron, among others. Giving an infant under 6 months cow's milk could cause severe illness.
As another, infants don't drink water. Drinking even small amounts can cause dangerous electrolyte imbalances. Even if they're dehydrated, they're only supposed to receive milk or formula.
It's like putting gas in your car. Your car is specifically made to run on gasoline. If you put diesel on, you're going to have a bad day. They're very similar and do many of the same things, but they are not interchangeable. Infants bodies can only run on breast milk or formula because it approximates breast milk closely enough. You can't just give them something else to give them nutrients, vitamins, and minerals.