While we can find them in CA year round, grapefruits are actually a fall/winter fruit. They are juicier and more fragrant this time of year. Squeeze your juice from scratch or buy a good quality fresh grapefruit juice (not a shelf stable one if you can help it).

Use simple syrup if you have it or would use it, but agave nectar is quick, easy, and distributes in cold liquids and has a more mellow sweetness in my opinion.