Cinnamon flavors lots of holiday drinks, from eggnog to mulled wine. Here it appears in a juicy punch that's delicious spiked with Grand Marnier or Cognac. Slideshow: More Party Punches
In a saucepan, boil the orange juice, zest and cinnamon sticks over moderately high heat until reduced to 1 cup, 8 minutes. Strain and let cool.
In a large glass pitcher, combine the orange reduction with the orange and grapefruit juices and the grenadine. Stir well and refrigerate until chilled, about 1 hour. Just before serving, pour in the grapefruit soda. Dust the orange slices with cinnamon and serve in the punch.