Make the simple syrup by heating the sugar and water in a small saucepan. Add 8 plums to the water, boil down. Once it becomes more liquid then add the other plums and take off the heat. Cool. (extra syrup can be saved for up to 3 days in the refrigerator)
Fill your glass with desired ice. Fill the glass 3/4 full with soda. Add 1 cup of the syrup then pour over the cream and milk. Stir. Add garnish, for example, lime and extra plums.
For Italian Ice smoothies, add more syrup, whole plums, and ice. Blend gently. Freeze the remainder for popsicles.