Combine water, apple cider vinegar, sugar, and cranberries in a saucepan over medium heat, cook until the sugar is dissolved. Remove from heat, strain out cranberries and cool in a container until ready to use.

Pour about 1 oz of the chilled cranberry shrub into a glass, top with chilled prosecco and garnish with a fresh rosemary sprig and a few cranberries. Cheers!