01 - In a small saucepan, combine honey, lemon juice, water, raspberries or strawberries, and sugar if using. Gently mash the berries with a fork or muddler. Heat over low heat for 2 to 3 minutes, stirring continuously, until the honey dissolves completely and the mixture takes on a vibrant pink color.
02 - Pour the warm mixture through a fine-mesh sieve into a bowl or jug, pressing firmly on the fruit to extract maximum color and flavor. Discard the solids and set the syrup aside to cool slightly.
03 - Fill four serving glasses generously with ice cubes. Divide the pink honey-lemon syrup equally among the glasses, pouring about 2 to 3 tablespoons into each.
04 - Pour chilled sparkling water or club soda over the syrup in each glass, filling to the top. Stir gently to combine the syrup and sparkling water without losing too much carbonation.
05 - Garnish each glass with a lemon slice and a sprig of fresh mint. Serve immediately while cold and fizzy.