Prepare the Simple Syrup: In a small saucepan, combine equal parts granulated sugar and water. For example, use 250g (1 cup) sugar and 250ml (1 cup) water. Heat over medium heat, stirring constantly, until the sugar is completely dissolved. Do not boil. Remove from heat and let cool completely. Once cooled, transfer to an airtight container and store in the refrigerator for up to 2 weeks. This recipe requires 120-240ml (1/2 - 1 cup) of the cooled simple syrup.

Juice the Citrus: Squeeze fresh juice from 3-4 large oranges, 2-3 large grapefruits, 4-5 limes, and 3-4 lemons. Strain the juices through a fine-mesh sieve to remove pulp and seeds, if desired, for a smoother texture. You should aim for approximately 750ml (3 cups) orange juice, 500ml (2 cups) grapefruit juice, 120ml (1/2 cup) lime juice, and 120ml (1/2 cup) lemon juice.

Combine Base Ingredients: In a large punch bowl or beverage dispenser, combine the strained orange juice, grapefruit juice, lime juice, and lemon juice. Stir in the cooled simple syrup, starting with 120ml (1/2 cup). Mix well.

Taste and Adjust Sweetness: Carefully taste the citrus juice mixture. If it's too tart for your preference, gradually add more simple syrup, 30ml (2 tablespoons) at a time, stirring and tasting after each addition, until it reaches your desired level of sweetness. Remember that the sparkling water and optional wine will further dilute the flavor.

Add Effervescence: Just before serving, gently pour in the chilled sparkling water or club soda. Stir very gently to combine, being careful not to lose too much carbonation.

Add Sparkling Wine (Optional): If using, gently pour in the chilled sparkling wine. Stir very gently one last time to incorporate. Avoid over-stirring, which can flatten the bubbles.

Garnish the Punch: Add the sliced oranges, lime slices, and cranberries (if using) to the punch bowl. These add visual appeal and a subtle hint of flavor.

Serve: Ladle the punch into glasses filled with ice. Using large ice cubes or an ice ring (a mold filled with water and garnished with fruit) can help keep the punch cold without diluting it too quickly.