The original recipe calls for vinegar, which really could be any sort from wine vinegar to a cider or malt. As an accompaniment to meats & fish, though, I prefer to use a wine vinegar, and like to "tempre it vp" with extra wine (a personal decision but keeping in period). This imbibes a smoother, more mellow quality, and makes the sauce a little easier to accept, especially for those not used to such a combination of ingredients.
Although originally Galyntyne referred to jellied juices of meat & fish, the term eventually came to mean this sauce itself. Galyntyne is a wonderful condiment for grilled fish & roast pork.
Take crustes of brede and grynde hem smale. Do şerto powdour of galyngale, of canel, of gyngyuer, and salt it; tempre it vp with vyneger, and drawe it vp şurgh a straynour, & messe it forth.
Take crusts of bread and grind them small. Add powder of galyngale, of cinnamon, of ginger, and salt it; mix it with vinegar, and pass it through a strainer, & serve it.
Hieatt, Constance B. and Sharon Butler. Curye on Inglish: English Culinary Manuscripts of the Fourteenth-Century (Including the Forme of Cury). London: For the Early English Text Society by the Oxford University Press, 1985; Gode Cookery