1Spray 5- to 6-quart slow cooker with cooking spray. In slow cooker, mix sweet potatoes, onions, garlic, chili powder, cumin, tomatoes, refried beans, black beans and broth.
2Cover; cook on Low heat setting 7 to 8 hours (or on High heat setting 3 hours 30 minutes to 4 hours).
3Before serving, stir in vinegar. Serve chili with cheese and sour cream.