I have transcribed the following for you from “A Miscellany by Cariadoc & Elizabeth” (a privately published volume about the middle ages for ‘living history’ afficionados). I have also seen (not yet tried) an equivalent recipe
for a raspberry-vinegar drink.
Dissolve 4 cups sugar in 2-1/2 cups of water. When it comes to a boil, add 1 cup wine vinegar. Simmer 1/2 hour. Add a handful of mint, remove from fire, let cool. Dilute the rsulting syrup to taste with ice water (5 to 10 parts water to 1 part syrup.) The syrup stores without refrigeration.
Note: This is the only recipe in the Miscellany based on a modern source: _A Book of Middle Eastern Food_, by Claudia Roden. Sekanjabin is a [pre-1600] drink; it is mentioned in the _Fihrist_ of al-Nadim, which was written in the tenth century. The only [pre-1600] recipe I have found for it (in the Andalusian cookbook) is called “Sekanjabin Simple” and omits the mint. It is one of a large variety of similar drinks described in that cookbook–flavored syrups intended to be diluted in either hot or cold water before drinking.