Divide the strawberries and basil. Place 3–4 strawberries and 3 basil leaves in each glass.
Muddle gently. Use a muddler or wooden spoon to press the fruit and basil together. Aim to release juices without turning everything into mush.
Add ice. Fill the glasses with ice to cool everything down and hold the muddled mixture in place.
Top with sparkling lemon beverage. Pour the cold lemon beverage over the ice, dividing evenly between the two glasses. Stir gently once or twice to mix.
Garnish and serve. Add a lemon slice, half a strawberry, and an extra basil leaf on top. Sip immediately.
Bold tip: Muddle lightly — you want juice and aroma, not a puree.