i agree with the match in the water but if that doesnt work they say to use a lemon put some sugar on it.hiccups are caused by The diaphragm almost always works perfectly. When you inhale, it pulls down to help pull air into the lungs. When you exhale, it pushes up to help push air out of the lungs. But sometimes the diaphragm becomes irritated. When this happens, it pulls down in a jerky way, which makes you suck air into your throat suddenly. When the air rushing in hits your voice box, you're left with a big hiccup.
Some things that irritate the diaphragm are eating too quickly or too much, an irritation in the stomach or the throat, or feeling nervous or excited. Almost all cases of the hiccups last only a few minutes. Some cases of the hiccups can last for days or weeks, but this is very unusual,but i would try the lemon with sugar if that doesnt work it could be more more serious.you may have tried this already but if not at least give it a try what can it hurt.