Here is a link to a website:
http://www.refluxmd.com/learn/resources/2013-05-01/2427/apple-cider-vinegar-acid-reflux
It suggests using 1 teaspoon to 2 tablespoons mixed with 8 oz. of water with meals or when you have heartburn. You can mix in 1-2 tablespoons of honey if desired to make it taste better. If you prefer to drink it straight, know that it will erode your tooth enamel, so it's better to sip it thru a straw.
I'll be starting this myself today.