Start by pouring the chilled Fanta and Sprite into separate ice cube trays, filling each compartment about three-quarters full. Place the trays in the freezer and allow them to freeze for at least 4 hours or until solid.

In a large pitcher, combine 2 cups of chilled Fanta and 2 cups of chilled Sprite. Pour in 1/4 cup of grenadine syrup followed by 1/4 cup of fresh lemon juice. If desired, add a few dashes of Angostura bitters for extra depth. Stir gently until everything is well incorporated.

Transfer the drink mixture into a blender and add a generous handful of the frozen Fanta and Sprite cubes. Blend on high for 30 to 45 seconds until you achieve a thick, slushy texture.

Once you have the ideal slushy consistency, gently mix in sliced cucumber and lemon wedges. Let the mixture sit briefly to meld the flavors.

Scoop the slushy mixture into tall glasses. For a stunning presentation, add additional cucumber slices and lemon wedges as garnishes. Serve immediately.