We've got a great existing question on how to avoid Delhi Belly, but what happens if you're afflicted with it but still need to travel? For example, you have a non-changeable travel booking, or your visa is about to expire and you just need to leave the country. In such a case, staying put in your accommodation near the bathroom isn't an option...
In the situation where you just need to travel, what can you do to minimise your problems while you're suffering from a GI infection?
I have tried the medicines such as imodium that are designed for this and they make me feel very unnatural and uncomfortable so I personally don't use them. I'm sure they will be dealt with in other answers. Others who prefer something more natural recommend charcoal tablets but I have not tried those.
Naturally I avoid moving when afflicted but this is what I do if I don't have a choice about when to travel:
Choose a more luxurious way to travel if you can.
If you have to move on a certain date but don't already have your ticket you can take a step up in your usual comfort level. Switch from bus to train, or switch from chicken bus to VIP bus, or switch from 3rd class train to 2nd class. This is best when it means it increases your chances of getting transport with a toilet.
Pack lots of toilet paper in your daypack / carry-on luggage.
Spare underwear and hand sanitizer etc are never a bad idea.
I eat lots of plain dry bread before and during the trip.
Not sandwiches with butter or buns with sugar. No meat, no cheese, just plain. I find bananas are also pretty good, at least for me.
Avoid drinking too much water.
This is a bit tricky because one of the bad effects of the condition is dehydration, but if you have a nasty case then even drinking anything can sometimes go straight through you.
Take a bottle of water on the trip in case you feel the dehydration could become a bigger problem at some point and is worth the "risk". Do not take drinks with sugar or anything else like orange juice or milk or Coke. Black tea might be OK but coffee seems to make things worse. Personally I find drinking yoghurt very good. Perhaps because it has probiotics and does not have lactose, despite popular belief.
Be very sure it's "only" Delhi Belly.
Not every cause of "the runs" is a mere inconvenience. There are some serious conditions you can pick up travelling that also result in diarrhea but for which you should make emergency changes to your plan and use your travel insurance or your emergency money.
Do not travel if you have amoebic dysentery - go to a hospital.
Firstly, we'll start with an acronym so that we don't have to use it again. Henceforth, TD will mean Traveller's Diarrhea.
Now that that's out of the way, let's look at what happened. You likely ate, or drank something that has caused your innards some grief. It may have even come from a surprising source that you don't immediately consider - ice cubes in your drink, or water while brushing your teeth.
The most common cause is a source of bacteria, in particular E.Coli, but many similar microbes can lead to stomach distress and TD.
It's important to be aware that there are also more serious forms with very similar symptoms, including:
Right, so I've got TD, but can't rest and need to travel - now what?
Symptoms frankly often clear up after a day or two on their own. This of course is of little comfort when you're suffering, but at least there's hope, a light at the end of the TD tunnel. You can also speed up recovery through:
Above all, monitor and listen to your body. TD is more often frustrating and awkward than dangerous, but you need to look for symptoms of it progressing or getting worse, and in any event of further symptoms developing, speak to a medical professional.
Apart from all the useful information given in the answers above, you can carry a pack of Adult diapers. (http://www.healthkart.com/personal-care/elderly-care/adult-diapers?navKey=SCT-pc-dia). A friend of mine had a similar situation about 8 years back when we didnt have these diapers available at ease so he had to just use a largest baby one, somehow and just kept on changing whenever possible.
I originally made this a comment to one of the other answers, but I decided to make it more detailed, with explanation of the medication you can get. It falls into several groups:
Anti-diarrhetics: Namely Imodium, are good at stopping the diarrhea, but not good at curing the disease itself. An analogy is taking painkillers for toothache, it doesn't quite solve anything. It can be good, however, during the journey itself, because it eases the conditions. However, it knows to make people feel strange.
Anti-biotics: You have 3-day multi-spectral anti-biotics that some people carry on every journey like Azithromycine, these may help if the cause is bacterial. Or you can get some of these prescribed. I wouldn't recommend taking anti-biotics for diarrhea without the recommendation of a doctor.
Intestinal desinficiens: These are really densinficiens and they can help with various bad stuff in the system. One such is Endiaron/Chloroxin/Capitrol.
Absorbents: Substances capable of absorbing stuff and preventing it from getting into the blood system. They basically clean the stomach and bowels' walls of remains of other stuff. The most commonly known in charcoal; if you decide for it, remember that a standard dose is 4-6 tablettes and you should crush them before eating; it's a bit disguisting to eat charcoal powder, but it works. From my own experience, much more efficient is Smecta/Smecdral/Diosmectite, it's basically a purified dirt (actually it's silicates), and has the same effect as charcoal; it's a grayish powder that has to be mixed with a small amound of water (about one noggin, mix it well since it's not solvable in water) and drunk as a shot (because it's really yuck to drink). The good thing about this method is that it helps to get whatever bad is there out.
If you asked me, I would take maximal recommended dosage of Smecta. For the journey itself, I would consider Imodium to ease the journey. Of course, you may phone your general practitioner and ask him for advice. Other than that, good diet is important: black tea with no sugar, non-sparkling mineral waters (you lose fu**ing lots of minerals by diarrhea), dry white bread/rolls, well-cooked rice, black chocolate (it is a perfect source of energy that "slows down"), bananas (moreorless the only fruit that is not acid, it's fibres help to clean up). The amount of liquids you need to get is much higher because you lose a lot of liquids.
Last but not least, I won't repeat what other have said, just one thing to emphasize: Remember that diarrhea can be much more serious than one thinks.
