Mix the granulated sugar and ground cinnamon together on a small, flat plate until well combined.

Wet the rims of four champagne flutes using a small amount of water, apple cider, or a lemon wedge.

Dip the rims of the flutes into the cinnamon sugar mixture at an angle to coat the edges evenly.

Pour approximately 2 ounces (1/4 cup) of chilled apple cider into each prepared champagne flute.

Carefully top each glass with the chilled Champagne or Prosecco, pouring slowly to prevent overflowing.

Garnish each glass with a thin apple slice and a cinnamon stick, serving immediately while carbonated.