Hiccups are caused by a spasm of your diaphragm. If you take a very deep breath, and continue to "sip" in air to continue to fill your lungs past the point you thought you could, you will work/stretch/contract your diaphragm so hard that it will be impossible to hiccup. Hold that breath for as long as possible (without passing out of course) and you are treated. You almost never have to do this more than twice or thrice to stop the hiccups.

One thing that works better is eating a teaspoon of peanut butter but PBJ is not always at your disposal is it?

(AW- Anil)