Combine 4 cups water and sugar in a large saucepan; bring to boil.
Cook until sugar dissolves, stirring occasionally.
Pour over tea bags. Cover and let stand 5 minutes; discard tea bags.
Cool. Stir in juice, vodka, and Grand Marnier; Let Chill.
Gently stir in ginger ale. Serve over ice. Garnish with cranberries and orange slices if desired.