Bring the apple cider, water, 1/2 cup sugar and 1/3 cup sea salt to a boil in a small saucepan. Stir until sugar and salt dissolves. Remove from heat and add a few ice cubes to cool the brine. Allow to cool completely then add to the bags with the pork chops along with the rosemary sprigs, garlic cloves and black peppercorns. Refrigerate for at least 4 hours up to overnight.