In slow cooker, combine beef, peppers, onion, fajita mix and water. Cover and cook on low 5 to 6 hours or until meat is tender.
Warm tortilla in microwave according to package directions. With spoon, lift meat mixture out of pot. Place about 3/4 cup mixture along center of each tortilla. Top with chopped tomato, sour cream and avocado. Fold both sides over filling.
By Patricia Ralston from Houston, TX