Bring the water to a boil in a large pot, and remove from the heat. Immediately whisk in the sugar and lime juice until sugar is dissolved. Add the tea bags and cranberry juice. Allow the tea to steep for 10 minutes, remove the tea bags and cool the tea. Stir to be sure that the sugar is dissolved, and place in a large pitcher. Refrigerate until thoroughly chilled.

Just before serving, add the vodka to the tea and serve in tall glasses filled with ice. Garnish with lime slices.