I am asked all the time how I make my Shrub in the store, the follow is what I do.
Chose your Balsamic Vinegar. I will frequently use a mixture of White Balsamic Vinegars, Pineapple, Coconut and Key Lime. I mix the vinegars together then I add them all to the pitcher first, put either ice or re-freezable cubes over them, and then add carbonated mineral water such as Perrier. I will dilute the vinegar to my taste. I will put the balsamic in the refrigerator for a bit if I know that I have time before serving just to help it cool.
That is it, it is that simple and makes a great refreshing drink.