To make pickled jalapenos, combine 3/4 cup of water, 3/4 cup of distilled white vinegar, 3 tablespoons of white sugar, 1 tablespoon of kosher salt and 1 crushed clove of garlic in a saucepan over high heat. Add 1/2 a teaspoon of oregano, and then bring the mixture to a boil. Stir in 10 large sliced jalapeno peppers, and then remove the saucepan from the heat. Pack the peppers into jars, cover with the vinegar mixture, and refrigerate.
For the best flavor, marinate the pickled jalapenos in the refrigerator for a few days before eating. Store pickled jalapenos for several months using this preparation method.
To make pickled jalapenos that remain good for one year or more, use water-process canning to sanitize the jars of jalapenos. After packing the jalapeno and vinegar mixture into jars, insert each jar into a pot of boiling water. Ensure that at least 1 inch of water covers each jar, and then put a lid on the pot and let the jars boil for 12 minutes. After 12 minutes, turn off the heat, remove the lid of the pot, and then let the jars sit for another five minutes.
Use a jar lifter to remove the jars from the pot, and set them on a towel. Within 30 minutes, the lids of safely sealed sometimes make popping noises when they seal. Let the jars cool for at least 12 hours before opening.