Peel the potatoes, carrots, onions, garlic cloves, and green or red apple. Slice them, along with the green peppers and the celery rib, into equal-sized pieces about ½-inch big. Throw them in tall, empty stainless steel pot or an enameled Dutch oven.
Crush the dried sweet pepper by hand and tear it up into a dozen or so equal-sized pieces. Add the low-sodium canned beans, sauerkraut, bouillon cube, sweet mustard, apple cider vinegar, and chili flakes to the pot. Drown in equal parts lager beer and water.
Set the heat on your stove to medium-high, bring to a rolling boil, lid on, and give your stew-in-the-making an initial stir. Crack open the lid, lower the heat to medium, and let simmer for 1½ hours.