Drain beans, reserving 1/2 cup of liquid. Rinse beans and drain again.
Combine beans and reserved liquid in a small saucepan and heat over medium heat until simmering. Simmer 4-5 minutes or until heated through. Cover and set aside to keep warm.
Meanwhile, heat a nonstick griddle over medium heat. Warm each tortilla on the griddle for about 1 minute each side, or until hot but still soft. Place on plate in oven to keep warm. Continue until all the tortillas are heated. Cover plate of tortillas with foil.
To serve, spoon some beans down center of hot tortilla. Place a few slices of avocado along the beans. Add any other garnishes as desired, such as cheese or lettuce. Top with a tbsp each of sour cream and salsa and a few leaves of cilantro, if desired. Fold up and eat while still hot.