Your Onion Rings Are Sorely Missing A Vinegar Boost - Tasting Table
Briefly

If you want to level up the onions for your fried rings, you can do even more of a pickling than a vinegar soak. Try these sugar-free pickled red onions for a great onion ring base... You could also use jarred pickled onions, but they would best be suited to a recipe that's lightly battered for thinner slices of onion, like shoestring fried onions.
The addition of vinegar balances any heaviness from the batter. Vinegar will also wash away the sulfurous compounds of the onion, making it more tender, and giving it a fresh, tangy flavor.
You can soak the rings of onion in the vinegar of your choice for anywhere from 15 minutes up to an hour. Be mindful of just how much tang you want: Higher acidity vinegar like balsamic or wine vinegar will deliver a more sour punch.
This 'quick pickling' method is perfect for last-minute doctoring of onions for any use, and red wine vinegar or balsamic will also add beautiful color to the onions.
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