Combine avocado and lime juice, tossing to coat.
Heat oil in a medium saucepan over medium-high heat. Add garlic; sauté 1 minute. Stir in water, cumin, and beans. Reduce heat to medium; simmer 3 minutes or until thoroughly heated, stirring occasionally. Warm tortillas according to package directions. Spoon 1/4 cup bean mixture into each tortilla. Top with 1 1/2 tablespoons sour cream, 1 1/2 tablespoons salsa, and 2 tablespoons avocado; roll up.