Step 1

Whisk vinegar, water, sugar, and salt together in a saucepan and bring the pickling liquid to a boil. Cook until the sugar and salt are fully dissolved then remove from heat and let the brine cool to room temperature.

Step 2

Place onion slices in a sealed container and add the vinegar mixture until covered. A 1 quart mason jar works perfectly for this.

Step 3

Let sit for at least 1 hour, but it is best if left in the fridge overnight.