Add the pork pieces, onions, carrots, celery, red bell peppers, and garlic to the crock-pot.
In a small bowl, mix together the juice of the canned pineapple, soy sauce, vinegar, cornstarch or flour, sugar and sugar substitute, ginger and red pepper flakes. Mix well until everything is dissolved. Using a wire whisk or fork helps to incorporate the cornstarch. Pour sauce over pork and vegetables. Add canned pineapple chunks and mix well. Cover.
Cook on high heat for 2¾ hours or on low heat for 5½ hours. Note: Every brand of crock-pot is a little different so the time may vary a bit.
Just before serving, add cabbage to a microwave-safe bowl and cook in microwave for 2-3 minutes until soft.
To serve: Divide cabbage among 5 bowls or plates. Top each with about 1 cup sweet and sour pork.
This dish freezes great. Mix together the pork and cooked cabbage and freeze in individual servings.