Combine all ingredients in a large pot over medium heat. Stir to dissolve sugar as mixture warms. When the wine starts to steam and is very hot to touch (about 10-15 minutes), turn off the heat. Don't let it simmer or boil. Taste and add more sugar if desired (it will depend on the sweetness of the wine - you may like to add a few more tablespoons). Strain any leftovers and refrigerate, covered.