Combine all the ingredients in a small saucepan over medium heat for 3 to 4 minutes until the rhubarb is submerged in its juices and the liquid is bubbling over.
Pour into a food processor or blender and mix until smooth.
Strain into an airtight container. Makes about 1 cup.
Add the whiskey and rhubarb puree to a cocktail mixer and add ice. Shake until the outside of the shaker is frosty.
Pour everything (including the ice) into a highball glass (a tall 10 to 12-ounce glass) filled with fresh ice. Pour the Fuji Apple Dry Sparkling Soda over everything and serve with straws.