Pickling those watermelon rinds will not only ensure that you use up every last bit of this summer staple, but they'll also give you another way to love on watermelon for months after the last ray of summer sunshine disappears. Brine the rinds overnight in a mixture of salt and water. The next day, combine water, vinegar, lemon juice, sugar, and spices, and boil them to make your vinegar brine. Drain and rinse the watermelon rinds, then add them along with the orange zest and lemon slices to the vinegar brine. Simmer them for 40 minutes, but make sure the brine doesn't cook down to syrup.