Cut the onions from the bottom all the way back up to the root and slice them as thin as possible.
Separate the onion slices and put them in a container like a mason jar or glass jar.
In a pot, bring 2 cups of red wine vinegar, 1 cup of plain water, 1-2 bay leaves, fresh garlic, peppercorns, and 1-2 tablespoons of sugar to a boil.
Immediately pour the brine over the onions, filling the container to the top.
Cover the container with cheesecloth or a paper towel and refrigerate for a couple of hours or overnight.
The pickled onions can last in the fridge for about 2 weeks.
