01 -
In a shaker or sturdy glass, muddle the watermelon cubes, mint leaves, and sugar (if using) until well broken down and fragrant.
02 -
Add lime juice and rum to the shaker and stir to combine.
03 -
Fill a glass with ice and strain the mixture into the glass.
04 -
Top with club soda and gently stir.
05 -
Garnish with extra mint, a wedge of watermelon, and a lime slice. Serve immediately.