1cupdistilled white vinegarcan substitute with apple cider vinegar
2cloves of garliccan be minced or whole
1teaspoonred pepper flakesoptional
Slice the onions as thinly as possible - I typically use sharp cuts on my knife or a mandoline slicer. Place garlic, red pepper flakes, and sliced onions in a jar with a tight fitting lid
Add the vinegar, water, sugar, and salt in a small saucepan over low to medium heat and heat - keep stirring until the sugar and salt dissolve completely (this takes about 1-2 minutes depending on your stove).
Pour this liquid into the jar with the onions, and let it cool down to room temperature (about 10 minutes) and then chill in the fridge, at least 30 minutes. Your pickled onions are ready to go!