I have found this to be 100% effective. I don't eat sugar, but if I have hiccups, one or two packages of splenda stops it immediately. I understand Sugar works too. Of course most of us here avoid Sugar and splenda - but it works for me when nothing else has.
I love spicy foods, eat a lot of them, but get the hiccups fairly often when I do. What works for me is drinking a glass of water straight down. One glass of non-stop drinking usually does the trick. I've had my son and my fiance try it and it's worked for them both.