Make simple syrup: Bring 1/2 cup each sugar and water to a simmer in a small saucepan, stirring, until dissolved; let cool completely. Combine 1/2 cup blood orange juice and 3 ounces each simple syrup and gin in a liquid measuring cup. Refrigerate until ready to serve. Divide the juice mixture among 8 flutes and top with chilled champagne or sparkling white wine.
Photograph by Ryan Liebe