Pour 1 gallon of the 2 ½ gallons of water into a large pot and add all of the remaining ingredients. Bring to a boil over high heat making sure all the salt and sugar is dissolved.
2 ½ gallons water, 3 cups apple cider, 3 cups kosher salt, 1 cup dark brown sugar, 2 lemons, 2 medium onions, 1 head garlic, 1 bunch thyme, 6-7 sprigs rosemary, 5 bay leaves, 2 Tablespoons black peppercorns