Chill the glass: Place a martini or coupe glass in the freezer for at least 10 minutes. A cold glass keeps the drink crisp.
Prep the rim: On a small plate, mix 1 tablespoon coarse sugar with a pinch of ground cinnamon.
Lightly drizzle caramel sauce around the rim of your chilled glass, then dip it into the cinnamon sugar. Set aside.
Build the cocktail: In a cocktail shaker, add 2 ounces vodka, 2.5 ounces apple cider, 0.5–0.75 ounce caramel sauce (to taste), 0.25–0.5 ounce fresh lemon juice, and 0.5 ounce apple liqueur if using.
Add ice and shake: Fill the shaker with ice. Shake vigorously for 15–20 seconds until the outside of the shaker feels very cold and the caramel is fully incorporated.
Strain and serve: Double strain into your prepared glass to catch any pulp or ice shards.
The drink should look silky and slightly frothy on top.
Garnish: Add a thin apple slice to the rim, a light dusting of cinnamon, or a small caramel drizzle over the top. Serve immediately.