Using a jigger, combine ¼ ounce of fresh lemon juice, ½ ounce of lemon simple syrup, 3 basil leaves, and, if making adult version, spirit of choice into a cocktail shaker. Muddle until ingredients are incorporated. Add ice, shake, and double strain into desired glassware. Top with ice and fill to top with S.Pellegrino. Garnish with lemon wheel and fresh basil leaf.