Combine the ingredients for the pickling liquid and simmer until the sugar and salt have dissolved and the brine has begun to boil.
Wash and sterilize a 16 oz. jar and lid by filling it with boiling water or running it through a cycle of the dishwasher.
Remove the stems and tips of the jalapeños and slice into rings about ¼ inch thick.
Fill the jars with the rings.
Cool the brine slightly, then pour it over the jalapeño slices to fill the jar, leaving about ½ inch of headroom.
Add a lid and store the jar of pickled jalapeños in the refrigerator.