In a small pot, bring the vinegar, beer, sugar, and salt to a boil to dissolve the sugar and salt. Once mixture starts to boil, removed from the heat and carefully pour the mixture over the onions.
Allow flavors to combined for 1 hour before serving.
Onions can be stored in a glass jar in the refrigerator for several weeks.
Extras:
Additional toppings like peppers and garlic can be added to the liquid or added to the jar with the sliced onions.
Recipe by Life Food and Beer at http://lifefoodandbeer.com/ipa-pickled-red-onions/