Microwave vanilla bean and 2 teaspoons water in a small microwave-safe bowl until softened, about 30 seconds.
Bring sugar and remaining water to a boil in a saucepan. Split vanilla bean lengthwise on a work surface; scrape out seeds with the back of a knife. Add seeds and pod to saucepan; boil until syrup is thickened slightly, about 2 minutes. Remove from heat and cool to room temperature.