Hiccups are noting but involuntary contractions of the diaphragm. Now how do you get rid of the hiccups fast? Since the diaphragm is controlled by the vagus, anything which increases the carbon dioxide in the system can relax the diaphragm and help you get rid of your hiccups. So the normal household techniques we try is drink a glass of water quickly. So the logic behind that when you drink the water quickly, you cannot breathe at the same time. So the carbon dioxide needs to go up a bit. The other things which you need to try is pinch your nose and keep on swallowing or make somebody scare you so that for a moment you do not breathe enough, so the carbon dioxide can still go up a little or if it is a little more persistent hiccups what can be tried is that you can cover your nose with a cover, with a plastic or air tight sealed cover and re breathe into it . You breathe in and out into the same cover so that the oxygen levels comes down and thee carbon dioxide levels go up which can relax the diaphragm and help you get rid of hiccups. You can even use smelling salts, but if the hiccups lasts more than 3 hours you should go to an emergency, because then you need medication supervised by a doctor.