What do giant swallowtail butterflies eat?

You can give them some necter I guess. Just put some water with sugar in it,mix it until the sugar dissolves and put some coiled cloth in something and pour the necter (a little until its wet) and that's it!you can also try putting in some flowers with necter in it. You can also try giving it some Oranges cuz my science teacher had some butterflies and she gave them half of an orange. Hope this will work!