Prepare the marinade.
OPTION 1 - Pickled onions ready in 12 hours.
Mix all ingredients (except water) in a container that can be covered with a lid and stored in the refrigerator. Put onions in the container, mix well, cover and marinate overnight in the refrigerator. These pickled onions are perfect for serving in sandwiches, especially those with rich meats, like pulled pork; you use them as a condiment to top tacos, bean dishes, barbeque, and plenty of other meat and fish dishes.