Slow cooker sweet and sour kielbasa is a flavorful and easy-to-make dish that is perfect for parties or weeknight dinners. Kielbasa sausages are cooked in a tangy and slightly sweet sauce made with ketchup, brown sugar, vinegar, and spices. The slow cooking process allows the flavors to meld together, resulting in tender and delicious sausages. Serve the sweet and sour kielbasa as an appetizer or as a main dish with rice or mashed potatoes.