Meh, then yeah you best drink pleanty of fluids if you have a bad case of diherea, lest you dehydrate. Also, something to repleanish some of the electrolytes, such as Gateraid, or some other such drink. When I was badly sick in the past and stuff, the doctor suggested I get some stuff (I'm not sure what you'd get it as, as they made it there), which essentially included various salts such as KCl (or potassium chloride, which is used by peramedics in rehydrating people who have lost so much water their body can't absorb it in the normal manner anymore), table salt (NaCl), and a bunch of other stuff to help restore the bodies electrolytic balance.
That dissolved in enough water (and KCl, you do want that stuff dissolved in pleanty of fluids), should help with re-hydration. Perhaps a pharmacy there will have some idea what could be taken for this, else you can try one of the sports drinks. Though for this sort of dehydration, a higher concentration of potassium then sodium might help.
OK, a quick biology lesson here. I assume you've probably had biology in school and know something of how liquids diffuse over the cellular membrane. Heck when I was in high school, they had plastic tubing which served as a membrane from which osmosis and the like could be demonstrated.
When one loses a lot of water due to diherea, the water content in the blood goes down (as it's leaving the body and not getting replenished), and the blood thickens a bit. The amount of water in the cells grows greater, and so water diffuses into the blood stream to restore this balance. Actually however, there are salts involved in helping to mantain this. Sodium ions remain in the blood, which with a higher salt concentration tends to make water diffuse out of the cells. This is also why people are told not to drink sea water if they're out on a boat and are thirsty. The saline content of salt water is higher then that of blood, so it will actually dehydrate one...
However, potasium ions tend to collect in the cells themselves, which has the opposite effect, making the cells hypotonic to the blood itself. Potassium helps get water back into the body cells (which is why perimedics use a potassium salt in helping a person severly dehydrated).
Many sports drinks have a higher sodium content listed on the label, but it is possible to find some with a higher potassium content listed. Those are what one wants for helping to rehydrate after severe diherea...
BTW, you might be able to try some mild things like chicken broth, soup, or something that isn't too solid. That's easier on the stomach then a normal diet and could get some calories in, though whether you can stomach this now or not, I'm not sure...