In a small saucepan, combine 1 cup water and sugar over medium-high heat. Bring mixture to a boil, stirring constantly; reduce heat to low, and simmer, stirring constantly, until sugar is dissolved, 3 to 4 minutes.
Remove from heat, and add basil. Let stand for at least 10 minutes. (The flavor will intensify the longer the basil steeps.) 3. Strain mixture through a fine-mesh sieve into an airtight container, and refrigerate for up to 3 weeks.
Recipe by Victoria at https://victoriamag.com/sparkling-pink-grapefruit-cocktail-recipe/