First make the cranberry sauce by adding the cranberries, sugar, water, rosemary, and orange zest to a saucepan. Stir together, bring to a simmer, and cook over low heat until the cranberries burst.
Once the cranberry sauce is ready, remove and discard the rosemary sprig and set the sauce aside to cool. While the sauce is cooling, juice the orange.
Add the cooled cranberry sauce to a cocktail shaker and muddle the cranberries to release any of the remaining juice.
Then, fill the cocktail shaker with ice and pour in the fresh orange juice. Add the cocktail shaker lid so it is sealed. Then, shake together until the glass is frosted.
To make one cocktail, add 2-3 ice cubes to a glass and pour ¼ cup of the cranberry orange syrup from the cocktail shaker. Then, add ½ cup sparkling water and 1.5 oz gin to each glass and stir together.
Top each cocktail with desired garnishes such as dried orange slices, sugared cranberries, or fresh rosemary. Then, serve and enjoy!