What I do is take a big cup (I know, real specific...sorry) and fill it up to what looks like anywhere from 1/8 to 1/4 the volume with ACV. The, I add the water. I know that's not real specific but I don't think it has to be. Just be sure to dilute it at least 4X, if that makes sense.
HG products: AG Recoil, DevaCurl Set It Free