Add the apples and raspberries to a medium pot over medium heat. Fill the pot with water until it is level with the fruit and bring to a boil. Lower the heat and simmer until the fruit begins to soften, about 10 minutes. Once softened, use a wooden spoon to lightly mash the fruit, concentrating on the raspberries. Let simmer for 5 more minutes. Line a fine-mesh sieve with cheesecloth and put over a bowl. Pour the contents of the pot into the sieve and using the wooden spoon, press all of the moisture out and, if necessary, release the cheesecloth from the sieve and squeeze out the excess juice. Add sugar, to taste, and refrigerate until cold or serve over ice in glasses.