Combine vinegar, water, Sugar, and salt, whisk until Sugar and salt have dissolved. 1. * Add onions and jalapenos to pickling mixture, store in refrigerator for 2–3 days, stirring occasionally. onions will keep for several weeks in the refrigerator. 1. * These onions are served as table condiments for grilled Beef dishes. You may increase the heat by adding more jalapenos.