A snickerdoodle is a type of cookie made with butter or oil, sugar, and flour, and rolled in cinnamon sugar. Eggs may also sometimes be used as an ingredient, with cream of tartar and baking soda added to leaven the dough. snickerdoodle is a type of cookie made with butter or oil, sugar, and flour, and rolled in cinnamon sugar. Eggs may also sometimes be used as an ingredient, with cream of tartar and baking soda added to leaven the dough.