Cut sausage; fry until done (if bulk sausage is used, shape into small balls or break up as it cooks). Pare and slice potatoes and apples. Mix salt and sugar together and blend with cold water. Arrange layers of sweet potatoes, apples and sausage in baking dish. Pour some of the sugar mixture over each layer. Top with apples and sausage and add drippings. Cover. Bake in moderate 375 degrees oven until apples and potatoes are tender, about 45 minutes.