Add the kielbasa to a 6 quart crock pot. Pour the drained sauerkraut on top.
Then top with the onions, minced garlic, brown sugar, spicy brown mustard, salt and pepper.
Pour the beer on top. Cover and cook on low for 4-5 hours or on high for 2-3 hours.
Serve warm and enjoy!
Notes
Refrigerate the leftovers in an airtight container for up to 5 days. You can use chicken broth or apple juice instead of beer in this recipe if you prefer.