One that works for me is to imagine the biggest yawn you have ever done and try to blow that out of the water; if you are not in that mindset it will not work. For me this works around 75% of the time.
P.S. Sorry if I made you guys yawn this isn't a joke it really works.
Gulping water usually does the trick for me
Hiccups are caused by the difference in timing between your diaphragm and lungs. By swallowing/holding your breath/etc, you involuntarily stop breathing momentarily and the timing correct itself. Most of the time that is
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Try drinking upside down. Just sip some water and hold it in your mouth and bend down with the crown of your head facing the ground and swallow. Repeat 3 or 4 times.
If someone has the hiccups, get right in their face and yell at them, asking why they have hiccups and keep going and being obnoxious about it. They will get confused and the hiccups shoudl go away. My wife's boss did that to her and it worked really well.