Recipes:

Arnaldus de Villanova wrote several recipes for vinegar in his book Book on Wine, one of them is a quick method involve drying and grinding grape seeds and grape skins into powder and mix with good vinegar, repeat three times drying each time. After the final drying mix some of the powder into wine and the result will become vinegar. In the 14th century a method of making vinegar with controlled quality was developed called "Orleans Method".

High quality wine, barrel, and vinegar bacteria seed were carefully selected and aged for six months. A guild for vinegar and other condiment makers were formed around the same time. There does not appear to be distillation during that time so I would guess vinegar in the 14th century would be more similar to balsamic vinegar, malt vinegar, or apple cider vinegar than distilled white or wine vinegar.

An alternative of vinegar used during the medieval France was verjuice, which is a very sour juice of unripe grapes. They seem to be used interchangeably with vinegar in many cookbooks.

Literature:

Sources:

El vinagre, Valorado desde la Antiguedad, por Nuria Baguena: https://www.afuegolento.com/articulo/el-vinagre-valorado-la-antiguedad/285/

El Origen del Vinagre: Parras: https://vinagresparras.com/noticias/8_el-origen-del-vinagre

http://historiavinagrera.blogspot.com/

https://www.diariolibre.com/revista/el-vinagre-y-su-historia-de-la-cocina-DODL174214

http://www.lastoreras.es/origen-del-vinagre/

The Science of Cidermaking: Cider Vinegar: Part 6: Apple Juice and Cider Vinegar: Registered to Andrew Lea 1997, updated 2016. http://www.cider.org.uk/part6.htm