Place tea bag in a small teapot; add boiling water. Let stand, covered, for 3 minutes. Remove tea bag, squeezing gently, and discard. Stir in Grand Marnier, lemon juice, vodka, Simple Syrup, and bitters.
Pour tea into a mug. Serve hot. If desired, garnish with an orange slice and a cinnamon stick.
In a small saucepan combine sugar and water. Bring to boiling over medium heat, stirring until sugar is dissolved. (The syrup is done when it is completely clear and the surface is covered with bubbles.) Remove from heat; cool. Store, covered, in the refrigerator up to 2 weeks.