Trim fat from meat; rub seasoning mix over both sides of meat. Place meat in an electric slow cooker coated with cooking spray; add onion, vinegar, and green chiles. Cover with lid; cook on low-heat setting for 9 hours. Remove meat from slow cooker, reserving cooking liquid; shred meat with two forks. Combine meat and reserved cooking liquid; stir well.
Warm beans and tortillas according to package directions. Spread 2 tablespoons beans down the center of each tortilla. Spoon a heaping 1/3 cup meat mixture on top of beans. Top each with 2 tablespoons cheese, 2 tablespoons tomato, and 1 tablespoon sour cream; roll up.