Combine the grapes, sugar and water in a large skillet.
Bring to a simmer over medium-low heat and cook for 20 to 25 minutes, until the grapes have softened and broken down. Use a large spoon to smash the grapes against the side of the skillet. Remove from heat.
Place a fine mesh strainer over a bowl. Pour the grapes through the strainer to collect the grape juice concentrate. Press down with a spoon to extract as much liquid as possible from the grapes. Discard the grapes and set the concentrate aside to cool. You should be left with about 6 ounces total.
Fill a glass with ice. Pour 2 ounces of grape juice concentrate into the glass and top off with sparkling water or club soda. Insert a Red Vines Grape Twist into the glass, stir, and enjoy. Store leftover grape juice concentrate in the fridge.