Combine sugar and cinnamon on a shallow plate. Dip the rim of each glass in water, then dip into the cinnamon-brown sugar mixture, coating the edge of each glass.
Fill each Champagne flute 1/4 of the way up with cranberry juice. Fill halfway up with apple cider. Top with Prosecco and a few cranberries and diced apple pieces. Garnish with an apple slice.