In a large pitcher, combine the freshly squeezed lemon juice and granulated sugar. Stir well until the sugar is completely dissolved.
Add the 6 cups of water to the pitcher and mix until well combined.
If using, add the activated charcoal powder and stir until fully incorporated for a spooky color.
Chill the lemonade in the refrigerator for at least 1 hour to let the flavors meld.
When ready to serve, fill glasses with ice cubes and pour the lemonade over the ice.
Top each glass with a splash of sparkling water for a fizzy finish.
Garnish with lemon slices and fresh mint leaves before serving.