For the simple syrup: Bring the sugar and 1 cup water to a boil in a small saucepan. When the sugar is completely dissolved, remove the saucepan from the heat and cool the syrup to room temperature.
For the vodka tonic: Muddle the cranberries, orange peel and 1 to 2 tablespoons simple syrup (depending on how sweet you like your drink) in a rocks glass. Add the orange juice, vodka and orange liquor, fill 3/4 of way with the tonic and add ice cubes. Serve immediately. Reserve the remaining simple syrup for another use. It will keep in the refrigerator, covered, for up to 1 month.