Homemade Pomegranate Soda Kit

For the pomegranate syrup: In a small heavy saucepan, combine the pomegranate juice and sugar and bring to a simmer over medium-high heat. Reduce the heat to medium and cook until the mixture is thick and syrupy, about 30 minutes. Remove from the heat and allow the mixture to cool completely (the syrup will thicken as it cools). Stir in the lemon juice. Transfer the syrup to an 8 1/2-ounce glass jar with a tightly fitting lid. Refrigerate.