Hiccups are a spasm of the diaphragm. My kids got them a lot as babies, especially before they were born (that sure looked and felt funny!). While they can sometimes be triggered by something you ate or drank, sometimes, they seem to occur with no clear cause. Doing things that put pressure or reduce pressure on the diaphragm (drinking water, holding your breath) can help to interrupt the spasms, though sometimes, a hiccuping spell just has to be waited out.