Padang food from Sumatra is the staple of travelers, students, and people too lazy to cook for themselves in Bali. Cheap, delicious, and fast, you choose what you want from piles of meat, vegetables, tofu, and tempeh dishes and top it with spicy sambal. A meal that will leave you full as a tick costs about $2. It may not be the healthiest food in the world as 99% is fried in palm oil, but pile up the cassava leaves and jackfruit if you need to feel better about it. There are Padang restaurants all over Bali and they are easy to spot by the piles of plates in glass cases in the window. My favorite is Putri Minang on Jalan Raya in Ubud as it always has a great supply of veggies for the many hungry yogis.
Oh, and most Padang restaurants are open 24 hours a day, so it's also great after-bar food.