Put rosemary syrup into a TSA-approved plastic container. Place container and rosemary sprigs in a quart-sized, resealable plastic bag. At the airport: After passing through security, buy a ruby red grapefruit juice. Look for one with no added sugar or other ingredients.
On the plane:
Order a vodka with a splash of soda water. To this, add rosemary syrup and grapefruit juice and stir. Smack rosemary sprig between your hands to release the aromatic oils and place in drink.
- 1 cup sugar
- 1 cup water
- 3 rosemary sprigs
In a small saucepan, combine sugar and water and bring to a boil, stirring occasionally. Add rosemary, cover, and remove from heat. Let cool to room temperature, strain, and store in a lidded container for up to 3 weeks. Use extra in other cocktails after your trip, or to dress up a winter citrus fruit salad.