Fill a highball glass nearly to the top with fresh ice. Plenty of ice keeps the cocktail colder and slows dilution.
Pour the vodka over the ice, followed by the Concord grape juice. The drink should begin turning a rich purple color.
Add the fresh lime juice. You'll notice a bright citrus aroma that balances the sweetness.
Slowly pour in the chilled ginger ale. Pour gently along the inside of the glass to keep as much carbonation as possible.
Stir gently once or twice until the color is evenly mixed. Avoid over-stirring so the drink stays fizzy.
Garnish with a fresh lime wedge. Add a few frozen grapes if desired for extra color and to help keep the drink cold.
Serve immediately while the bubbles are fresh and the cocktail is well chilled.