Boil the vegetables. In a large pan with straight sides or a pot, add beer, liquid smoke, red pepper flakes, black peppercorn, garlic, cabbage, onion and a nice pinch of salt. Bring to a boil then lower to a simmer for 20 minutes.
Add vinegar and sugar. Meanwhile, add vinegar and sugar to the pan or pot with the cooked cabbage and onions. Stir until the sugar dissolves. Simmer another 15 minutes. Serve warm or chilled with tongs to shake off the excess liquid.