Preheat the oven to 180°C (approximately 350°F). Line the muffin tin with paper cups.
For the topping, heat the sugar and champagne, stirring constantly, until the sugar has dissolved. Stir in the sliced almonds.
For the muffins, mix together the flour, apples, raisins, cinnamon, baking powder, and baking soda.
In another bowl, whisk the egg slightly. Stir in the sugar, vegetable oil, buttermilk, and champagne until combined. Stir the flour mixture into the egg mixture until just combined.
Pour batter into the lined muffin tin. Top each muffin with 1 tablespoon of the topping mixture. Bake in the preheated oven for 20 to 25 minutes. Let the muffins cool in the baking tin for 5 to 10 minutes. Then, remove from the tin and serve warm.