Clean the jar, lid, and band; rinse well. Keep them warm while you prepare the brine (for example, set them in hot water or near the stove).

In a stainless steel saucepan, combine 1 cup distilled white vinegar, 1 tablespoon sugar, 1 teaspoon kosher salt (or pickling salt), and 1 teaspoon olive oil (optional).

Heat the mixture over medium heat until it comes to a boil. Remove from heat.

Pack about 30 small peppers into the warm jar, leaving about 1 inch of headspace from the top of the jar.

Carefully pour the hot vinegar mixture over the peppers, maintaining about 1 inch of headspace.

Remove any air bubbles by tilting the jar slightly and pressing the peppers against the opposite side of the jar to allow trapped air to escape.

Wipe the jar rim clean. Place the lid on the jar and tighten the band until it is snug (fingertip-tight).

Set the jar on the countertop to cool with about 1 inch of space between jars. Allow jars to cool and seal.

After about 12 hours, test the seal by pressing the center of the lid: a sealed lid will not pop back. If a jar is not sealed, refrigerate it and use.

Store sealed jars in a dark, cool cabinet or pantry for up to a year.