Think holiday flavors and colors: cranberries and orange juice; apples, pomegranate juice, citrus peel, and ginger; or go deep with frozen blueberries and green grapes.
There are at least two ways to make the syrup:
1) Macerate the fruit with sugar (or the sweetener of your choice) and let it sit to help the natural sugars thicken.
2) Or put your fruit, juice and other ingredients into a saucepan, combined with half as much sugar (two cups of fruit and ginger to one cup sugar, for example). Simmer until thickened, and then pour through a fine strainer, pressing the solids to squeeze out all the syrup.
Measure—by cup or by eye—how much syrup you have. Add that same amount vinegar. Try apple cider vinegar with apples, white balsamic or unsweetened lemon juice with the blueberries, red wine vinegar with the cranberries and orange. Mix. Taste. Feel the surprise of your shrub!
Now, for the punch: mix equal parts shrub and seltzer or bubbly water in a big beautiful bowl. Add lemon slices and other garnishes. Serve.