Add the gin, cointreau, lime juice, cherry syrup, and bitters to an ice-filled cocktail shaker. Shake for about 30 seconds to blend.
Pour into a tall glass filled with ice. Top off with soda water and garnish with an orange slice and a cherry. Sip, and enjoy!
*To make the cherry syrup combine the cherries and granulated sugar in a heavy, medium saucepan. Heat until the sugar dissolves and the cherries give up their juice. Simmer over medium-low heat for 15 minutes, smashing the cherries into the juices as they cook. Remove from the heat and strain into a container, pressing hard on the solids. Refrigerate until cold. The syrup will keep for a week, covered and refrigerated.