To a 16 ounce jar, or medium bowl, add the water, apple cider vinegar, sugar, salt, peppercorns, chile and garlic. Stir to dissolve sugar and salt. Add the red onion slices and set aside for 15-20 minutes. Longer, if desired. Serve on your favorite burger.
Store in the refrigerator for up to 1 week if not using right away.