Well, that depends on the types of ant. There are around 12,000 species of ants worldwide and there are a huge variety of things each kind of ant eats. Some eat sweets, some eat protein (like dead bugs), some even make a farm to grow their own fungus to eat.
The ants for ant farms are called Western Harvester ants. Knowing what your ants eat is a good idea; because of course you want to take the best possible care of your new little friends. It is rather easy to maintain an ant farm, but there are a few essential things that you definitely need to know. After all, maintenance and up-keep is only part of the equation. You want your ants to be healthy and happy; you want them to thrive in their new environment.
Western Harvester ants enjoy small pieces of fruits and vegetables, the fresher the better. So, apples, lettuce, carrot, granola and celery will really please your ants. Don’t overfeed the ants. They only need 1 or 2 small pieces every three days. Remove any uneaten food with tweezers to keep mold from growing in the ant farm that could harm your ants.
Now, just as important as the question, What do ants eat? is the question, What do ants drink? Just like pretty much every other creature mammal, insect, reptile, amphibian, etc on earth, ants need water to survive. However, they do not need very much. To give your ants water, you simply need to give them a few drops each day. The sand in the ant farm should not be saturated. In fact, you need to make sure that the water does not pool on top of the surface, otherwise your ants may drown. If you mix in a little sugar with their water once a week, your ants will love you. It will make them busy little beavers, so to speak you have not seen energy until you have seen some ants with a sugar buzz!