Wash the peppers carefully, remove stems, and slice them into rings or strips depending on how you plan to use them later.
Place garlic cloves, oregano, coriander seeds, and red pepper flakes into clean jars to create the flavor foundation.
Pack the sliced peppers into the jars, mixing different colors together for a visually appealing pickle mixture.
Combine vinegar, water, sugar, and salt in a saucepan, then warm the mixture until everything dissolves into a smooth brine.
Slowly pour the warm pickling liquid into the jars, making sure the peppers are completely covered beneath the surface.
Let the jars cool naturally before placing lids on tightly and moving them into the refrigerator.
Allow the peppers to rest for at least 24 hours before serving so the sweet and spicy flavors fully develop.