Preheat your air fryer to 390°F for about five minutes. Meanwhile, in a small bowl, combine the ground cinnamon with the white sugar, mixing well with a spoon or fork to create your cinnamon sugar coating. In a separate small bowl, pour the mulling spice syrup or apple cider concentrate. Set both bowls aside for later use.

Open the can of buttermilk biscuit dough and separate the biscuits. For each biscuit, use a biscuit cutter or bottle cap to press a hole in the center, creating a classic donut shape. Take the removed center pieces and roll them in your hands to form small donut holes. Carefully reshape the donuts if needed to make them even and round.

Hold each shaped raw donut over the bowl of cinnamon sugar, and using a spoon, pour the cinnamon sugar mixture over the entire donut to coat it thoroughly. Make sure all sides are covered, then set each donut and donut hole aside, ready for air frying. Repeat this process for all pieces.

Reduce the air fryer temperature to 350°F. Place the coated donuts and donut holes in the air fryer basket, leaving enough space between each one to allow for proper air circulation and rising. Air fry for 10 minutes. You may need to cook in batches so the donuts have room to cook evenly. I like to peek halfway through to ensure they're not overcrowding and adjust if needed.

After air frying, while the donuts and holes are still warm, dip each one into the mulling spice syrup (or apple cider concentrate) from Step 1, ensuring all sides are coated. Then, dip each donut again into the remaining cinnamon sugar mixture, covering all sides. This double-coating gives the donuts a sweet, spiced exterior that's especially tasty.

Serve the freshly coated donuts and donut holes while they are still warm. Enjoy immediately for the best texture and flavor! For an extra treat, I like to serve these with a cup of hot apple cider during the colder months.