To a pan on medium-high heat add water, blueberries and grated ginger. Let it all come to a boil.
Once the mixture starts boiling, add sugar and mix till it dissolves.
Now lower the heat and using the back of your spatula, mash the blueberries. Mash all of it and let the mixture simmer for another 10-15 minutes.
Remove from heat and once the syrup has cooled down, cover it with a cling sheet and let it sit at room temperature for 2-3 hours. This is important so that the flavors mix-in well.
After 2-3 hours, strain the syrup into a clear bowl. At this point you can cover and keep it refrigerate until ready to use.
To serve the blueberry ginger cooler, fill 2/3 of the glass with the syrup, add ice cubes.
And then add lemon-lime sparkling water on top and stir so that the soda and syrup combine well.
Garnish with some fresh blueberries and mint leaves and enjoy!