We took this cocktail on our annual Independence Day camping trip with friends. It was so easy to keep the ingredients separate in a cooler until cocktail hour, when we eagerly whipped up this garden-fresh drink for a quick cool-down. For a party-sized batch, you will need three cups of freshly-squeezed grapefruit juice (from about six grapefruits), three cups of basil-infused simple syrup, 750-ml. of your favorite gin or vodka, club soda and ice.
To make a Basil Grapefruit Martini: combine equal parts grapefruit juice, basil syrup, and gin/vodka over ice. Top with soda, relax, and celebrate!