Isn't the Diaphragm above the Stomache? Some foods are quite thick so it makes the Diaphragm contract and relax very suddenly so it makes you hiccup.

The vagus nerve controls many functions, including coordination of swallowing and breathing.  Branches variously control the back of the mouth and throat, including some taste sensations.  The vagus also coordinates the action of the epiglottis in passing food over the trachea without choking, and of the phrenic nerve in preventing inhalation while swallowing.  Hiccups arise from interference with nervous control of  that coordination. The diaphragm contracts suddenly, causing sharp intakes of breath, which the epiglottis abruptly shuts off at the top of the throat.

Pungent foods like strong pickled onions, chilli, fizzy drinks, anything irritating to the back of the throat or tongue, may confuse relevant branches of the vagus. Also, both phrenic and vagus nerves extend down the neck and might be affected when such foods, or dry materials that are hard to swallow, go down the oesophagus.  Nerve pathways and reactions vary in different people, and non-specific stimulation of nerves gives unpredictable results, so those very same stimuli are folk remedies for hiccups, stopping attacks by the same means as they start! Even without involving swallowing, blood vessels pressing on the vagus have directly caused inappropriate stimulation, resulting in hiccups persisting for years in some people. 

Perhaps because the food is spicy hot you tend to keep your mouth open longer whilst chewing taking in more air with your food and this trapped air is trying to escape..naturally.