Preheat the oven to 375 degrees. Cut the sweet potatoes in half. Cut the squash in half vertically and scrape out the seeds. Put the vegetables, cut side up, in a baking pan and bake, uncovered, until they are very soft, at least 1 1/2 hours. Scoop the potato and squash out of the skins, combine them, and mash until smooth. Put the orange juice, butter, and cinnamon sticks in a small saucepan and heat, reducing until it is about 1/4 cup syrup. Discard the cinnamon sticks and stir the orange syrup into the mashed vegetables.