Combine sugars, water in salt in a medium saucepan.
Split vanilla beans lengthwise with the tip of a paring knife. Using the back of the knife scrape the seeds from the pods and add them to the saucepan. Add the pods to the saucepan.
Place the saucepan over medium heat and stir until sugars are dissolved.
Let cool a bit and pour into an airtight container. Refrigerate overnight. Strain and discard pods.
To serve combine ½ oz. (2 tbsps) with 8 oz. (1 cup) chilled club soda.
Add syrup slowly to avoid foaming. Stir well. Or, add 4 oz. (½ cup) syrup to 1 liter of chilled club soda. (Again, add syrup carefully to avoid foaming.)