In a saucepan add equal amount of water and sugar.
Bring them to a boil and simmer for 2 - 3 minutes till sugar gets dissolved completely.
Turnoff heat and cool down at room temperature.
Refrigerate in a glass jar for further/ future use.
Take watermelon cubes in a mixer jar and blend it to a smooth puree.
Strain out pulp and seeds with help of a strainer. Extract juice in a jar/pitcher.
In another pitcher, crush mint leaves (5 - 7 times) with help of a muddler.
Next add in watermelon juice and simple syrup.
Squeeze out fresh lemon juice and mix well.
Now add club soda and ice cubes.
Garnish with some more mint leaves.
Serve chilled non alcoholic mojito.
You can make the sugar syrup and watermelon juice in advance and refrigerate. Whenever required add fresh lemon juice, sparkling water or soda, juice, and sugar syrup in desired quantity and serve fresh.