Fill a stock pot with 2" more water than needed to cover the tops of jars, and begin to bring to a boil.
Wash jars and lids throughly and sterlize either in dishwasher or boiling water.
Bring vinegar, water, salt, and sugar to a boil
Pack jars with garlic and peppercorns/coriander/mustard seeds (if using) and peppers
Pour boiling vinegar solution into each jar, leaving 1/2" headspace. Cap jars finger-tight with canning lids.
Place sealed jars in boiling water for 10 minutes. Remove from water and place on cooling rack for 12–24 hours. Check lids for seal (they should be concave and not click/flex when pressed). Store jars in a cool, dark place for up to 18 months. Refrigerate after opening.