Vinegar is alcohol that is turned into acetic acid by bacteria. What is the source of that bacteria? Apples. Apple cider vinegar naturally encourages the bacteria needed. Buy unpasteurised apple cider vinegar from the supermarket and use 1/4 cup of that in a bottle of wine. Put the mixture in a glass or ceramic container with the top covered with cheese cloth or anything that allows gas exchange but excludes fruit flies. Put in a dark room temperature place for at least 6 weeks and you have wine vinegar. Use this to make more. Use a coffee filter to clean out the sludge, there will be a lot at this point. The sludge proves it's still alive so it's a good thing, just not so much of it. The acid content will still be low at this point so filter the vinegar and bottle it loosely so gas can escape while it works. Acid content will continue to increase till you use it. The longer you leave it before using it, the better it will be.