Cut the starfruit into chunks and place in a blender. Blend on low until pureed. Strain the juice and discard any solids. Chill until ready to serve. Makes 2 1/2 cups of juice.
Simple Syrup
Mix sugar and water in a small pot. Bring to a boil just long enough to dissolve the sugar. Chill until ready to serve.
Spritz
Fill a glass with ice. Pour sake, syrup, and juice over ice and stir. Top with soda,, garnish with fruit, and serve.