In a large skillet combine the 2 cups water, sugar, ginger, and vanilla. Bring to boiling; reduce heat. Add half of the rhubarb. Cover and simmer 2 to 2 1/2 minutes or until tender. Using a slotted spoon, remove the cooked rhubarb and set aside, leaving ginger pieces in the skillet. Repeat with remaining rhubarb. Remove ginger pieces from cooking liquid. If desired, place liquid in an airtight container and chill up to 1 week. Add sparkling water for a homemade soda.