Hard ciders can range from bone-dry to rather sweet, so take a sip and adjust the simple syrup if needed.
1 cup aged rum
1 cup sweet vermouth
½ cup fresh lemon juice
¼ cup simple syrup
4 dashes Angostura bitters
½ red apple, very thinly sliced, plus more for serving
3 3x1-inch strips orange zest, very thinly sliced, plus more for serving
1 12-ounce can Somerset or Original
Combine rum, vermouth, lemon juice, simple syrup, and bitters in a large pitcher. Add 2 cups ice and stir until ice has mostly melted and punch is very cold. Stir in apple slices and orange zest; gently stir in cider.
Divide punch among ice-filled old-fashioned glasses and garnish with more apple slices and orange zest.
Do Ahead: Punch (without apple, orange zest, and cider) can be made 1 day ahead. Chill.