Wash and dice the rhubarb into small pieces, roughly 1 cm in size.

In a medium saucepan, combine diced rhubarb, honey, still water, and basil leaves. Bring to a boil, then reduce heat and simmer for 12 minutes.

Remove from heat and cool the rhubarb mixture for 10-15 minutes.

Strain the cooled mixture through a fine mesh sieve into a large bowl, pressing down on the solids to extract syrup.

In each glass, add about ½ inch of rhubarb syrup, then add ice cubes and top with sparkling water, stirring gently.