In a heavy saucepan, combine cocoa, cinnamon and water; stir or whisk until there are no dry lumps of cocoa. Stir and cook over medium heat until mixture comes to a boil. Reduce heat; boil gently, stirring often, for 5 minuutes or until mixture is thick and smooth. Cool slightly. Stir in vanilla and sweetener. Pour into a container or jar with lid. Cover and store in refrigerator for up to 3 weeks. Makes 1 cup syrup.