Start by preparing your toppings. In a small bowl, mix together sugar, ground cinnamon, and nutmeg for the spiced sugar coating and set it aside. For the maple glaze, whisk together powdered sugar and maple syrup, slowly adding milk until you achieve a smooth, pourable consistency.

In a large mixing bowl, combine all-purpose flour, baking powder, baking soda, salt, and spices. In another bowl, cream together brown sugar and unsalted butter using a hand mixer until light and fluffy. Gradually add the eggs, mixing well after each addition, then stir in the vanilla extract, sour cream, and canned pumpkin.

Cover the donut batter with plastic wrap and chill in the refrigerator for at least 3 hours, or overnight. Chilling helps firm the dough for easier shaping.

Roll out the chilled dough on a floured surface to about ¾ inch thick. Use a donut cutter to cut out the donuts, placing them on a floured baking sheet. Heat flavorless oil in a deep pot or fryer to 365°F - 375°F. Fry donuts in batches for about 45 seconds to 1 minute on each side until golden brown.

Remove the fried donuts using a slotted spoon and let them drain on paper towels. Toss half of the donuts in the spiced sugar while warm, and dip the remaining donuts into the maple glaze.