As in just about every country in Latin America, it’s essential to watch carefully what you eat and drink. Tap water is absolutely never safe to drink; be sure to check that any water served at a restaurant or hotel is agua purificada. Be particularly aware of salads and uncooked vegetables, and make sure meat, especially pork, is well cooked. Eating street food is standard practice for many veteran travelers, but someone just coming to Honduras  for a short stay may want to avoid it and save themselves a possible case of diarrhea.
If you do develop diarrhea, two courses of action are available: Eat as little as possible, drink a lot of water, and let the bug run its course (literally), or take medications such as Pepto-Bismol or Imodium. How effective Pepto is depends on what the problem is, while Imodium essentially serves as a cork—not really what your body needs, but extremely useful when you have to go on a bus or plane ride when sick.
Food poisoning is also relatively common. Although it may appear severe at first, with vomiting and uncontrollable bowels, the bug will pass in about a day. Hole up in a hotel room with a good book, a bottle of water, and maybe a few pieces of bread, and expect to feel a bit weak for a couple of days following the illness. If symptoms persist, see a doctor—you may have dysentery. It’s extremely important to stay well hydrated if you’ve got either food poisoning or diarrhea.