Mix together sugar and cinnamon. Pour cinnamon sugar on a saucer or plate. Make sure the circle of cinnamon sugar is bigger in diameter than the rim of your champagne glass. Pour apple cider onto another saucer. Dip the champagne glass in the cider, then in the cinnamon sugar mixture. Tap off any excess and turn glass upright.
Apple Cider Mimosas
Pour champagne glass two-thirds to three-quarters full with champagne. Top off with apple cider. Be careful pouring so not to mess up your cinnamon sugar rim! Garnish with an apple slice if desired. Serve immediately.