For the best results, use a high-quality sparkling apple cider. The bubbles are crucial for creating a light and airy texture. If you don't have oat flour, you can make your own by grinding rolled oats in a food processor until finely ground. Feel free to add chopped nuts, dried cranberries, or chocolate chips to the batter for extra flavor and texture. Store leftover bread in an airtight container at room temperature for up to 3 days.