Under natural conditions, elephants eat mostly grass, tree leaves, flowers, wild fruits, twigs, shrubs, bamboo, and bananas. Their main food is grass when it's available, along with some leaves. They spend about 80% of their day (16-18 hours per day) eating.
Some elephants can even be found eating mud out of the bottom of ponds. They do this because the clay at the bottom is rich in minerals which are hard to find in the wild. The clay is a quick way to replenish the minerals their bodies are lacking.
Sometimes elephants will even use their tusks to dig into the ground to pull up the roots of trees to eat. When the weather is dry and foliage is sparse, they will eat any foliage they can find. They will even knock over dead trees to eat the remaining leaves at the top and the roots buried in the ground.