Spray inside of slow cooker. Add onion, bell pepper and garlic to slow cooker. Place chicken on top. Pour beer over top, and then add the diced tomatoes, tomato paste, apple butter and chili seasoning mix. Lightly stir to combine. Cover, and cook on High heat setting 4 to 6 hours or on Low heat setting 6 to 8 hours. Shred the chicken with 2 forks. If chili seems too thin, remove cover and let cook while you make sweet potatoes.