Baby gacha will gain food any time any babies around them gain food, so raising them next to other babies until they can get on trough is an easy method of keeping their hunger up. Just don't leave render, as it prevents this method from working.
If you’re playing Genesis Part 2 and you come across a loot drop open it and one thing i’ve found on official is that some drops give lots of pipes, generator wires and water irrigation pipes which is basically free food for the gachas! You can also grind them for resources and craft them into other items/structures of your choosing aswell! Hope this helps.