In a blender, add the cubed watermelon. If using watermelon with seeds, strain the puree through a fine-mesh sieve to remove the seeds and achieve a smoother texture. Blend until the watermelon is smooth and free of any seeds.
Transfer the strained watermelon puree into an ice-filled pitcher or jar.
Stir in the sekanjabeen syrup and fresh lime juice, ensuring they are well incorporated with the watermelon puree.
Fill a serving glass halfway with the strained watermelon mixture from the pitcher.
Top up the glass with ginger ale, allowing the effervescence to combine with the flavorful watermelon mixture.
Garnish the drink with fresh mint sprigs for an aromatic touch.
Repeat the process for additional servings.
Serve the Watermelon Cooler with Sekanjabeen immediately and enjoy the refreshing flavours on a hot summer day.