Heat the water, sugar and grapefruit zest in a heavy pot over medium heat to dissolve the sugar. Bring the syrup to a boil, then simmer for 10 minutes. Cool.
Add the citrus juices to the cooled syrup, chill well, and process in an ice cream maker according to manufacturers directions. Keep in freezer until ready to assemble the CandyCane gift jar.
Cranberry Citrus Sorbet
Heat the juice from the grapefruit, oranges and lemons in a heavy pot over medium-high heat. Once the juice starts to simmer, pour in the bag of cranberries. Cook until the cranberries all pop and their juice is released into the citrus juice mixture (about 10 minutes).
Process through the fine sieve attachment for a food mill or through a chinois. Discard the cranberry peels.
Make a simple syrup by bringing the sugar, water and Grand Marnier to a boil and simmer for 10 minutes. Add the cranberry citrus juice, bring back to a boil, and simmer for 5 more minutes. Chill well and process in an ice cream maker as directed by the manufacturer.
Assemble in layers in a gift jar that seals. I include a small spoon or scoop tied to the jar with a ribbon.