Place blackberries, water, Splenda Sweetener, orange juice, and ground sage into a blender; blend until smooth.
Press mixture through a fine sieve into an 8” square baking dish. Discard solids.
Cover and freeze, stirring and crushing lumps with a fork every 30 minutes, for a total of 3 hours. Stirring is important to prevent the mixture from freezing into a solid lump. The texture should be ice crystals.
Serve immediately in chilled glasses, and garnish with fresh sage leaves if desired.