Prepare a water bath canner, half-pint or pint jars, and lids. Preheat the canner water to about 140 degrees F for a raw pack.

Put on gloves. Wash the serrano peppers, trim off the stems and blossom ends, and slice them into 1/2-inch rings. For milder peppers, split them lengthwise and scrape out the ribs and seeds before slicing. To pickle them whole, cut two slits in each pepper, one on each side, instead of slicing.

Combine the vinegar, water, salt, sugar, and garlic in a large stainless steel saucepan. Bring to a boil, stirring until the salt and sugar dissolve. Reduce the heat and boil gently for 5 minutes, then remove and discard the garlic.

Pack the peppers into hot jars, leaving a generous 1/2 inch of headspace. Add the Pickle Crisp to each jar if using.

Ladle the hot brine over the peppers to 1/2 inch headspace. Remove air bubbles, running the tool into the slits on whole peppers, top up the brine if the level drops, wipe the rims, and apply lids and bands fingertip tight.

Lower the jars into the canner, make sure at least 1 inch of water covers them, and bring it to a full rolling boil. Process half pints and pints for 10 minutes, adjusting for altitude (see notes).

Turn off the heat, remove the canner lid, and let the jars sit 5 minutes. Lift them out and cool undisturbed for 12 to 24 hours, then check the seals.