How do ants help people?
Ants help humans by cleaning up things that are left behind, such as food and dead bugs and animals. This also helps the soil, so that more plants can be planted and grow.
Fire ants will eat other ants. Army ants will also eat other ants and actually seem to specialize in raiding the broods of other ant colonies. In fact fire ants will eat almost any kind of insect they catch. Ants (Formicidae) are a very broad genus. Asking what do ants eat is like asking what do people eat. It depends on which ants.
Ants are attracted to sugar and do not die from eating sugar or sweet things. Most people think sugar kills ant because they try to exterminate the ants with sugar water. The water is what kills the ants. For example, if a bowl of sugar water is left out to kill ants, the sugar attracts the ants but the water drowns the ants.