In a large pitcher or mixing jug, combine the Cool Blue Gatorade, Sprite, grenadine, and lemon juice. Stir gently but thoroughly to blend the flavors into a cohesive mix.

Assess the hue of your mocktail—if you'd like a more vivid purple tone, incorporate a drop or two of violet gel food coloring and stir again until the color is uniform.

Serve immediately over ice in your preferred glassware. For a festive touch, consider garnishing with gummy candies or dry ice for a spooky effect.