Combine 2 cups fresh cranberries, sugar, and water in a saucepan. Cook over medium heat, stirring occasionally, 8 minutes or until cranberries begin to pop. Pour mixture through a wire-mesh strainer into a large pitcher, discarding solids; cool completely (about 1 hour). Stir in chilled club soda, fresh Key lime juice, and, if desired, vodka. Serve over ice. Garnish with Key lime slices and fresh cranberries.
Very refreshing, light beverage, great with or without the vodka. I would make this again for anything, doesn't need the holidays to be good. If you do make with vodka, note my tasters agreed it needed twice the alcohol is pack any punch.