An elephant spends between twelve and eighteen hours a day eating. It varies from species to species and from individual to individual. It also depends on what the elephant has available to it at that point in time. If available, an elephant will eat trees, grass, shrubs, etc. They are herbivores, so they get all their nourishment from the aforementioned food and other plants that are found around.
They also typically drink as much water as a household bathtub can hold - fifty gallons or so - a day.However, this eating habit is typically really good for other species. If a herd of elephants comes through and eats a few trees that are blocking sunlight in areas, grasses can grow for other animals to eat. In addition to that, an elephant can dig for water, giving other animals access to water in a drought.