If you were wondering how infectious doses were established then the answer is that they really do challenge volunteers with different doses of live bacteria except with particularly dangerous diseases. Cholera, as we heard, under medical supervision is not very dangerous and so they do use human volunteers. This paper isn't actually trying to establish the infective dose but is available online so you can look at it.
I like the way that the volunteers 'were required to pass a written examination to document their knowledge of cholera and the study design.'
Also note in the methodology how they neutralized stomach acid with sodium bicarbonate before administering the cholera. Rehydration used CeraLyte, a rice based oral electrolyte.
WHO and UNICEF publish their own reccomendations for oral rehydration therapy which is
2.6g of sodium chloride, 2.9g of trisodium citrate, 1.5g of potassium chloride and 13.5g of glucose per liter of water.
Gatorade has more sugar (about 4 times as much if my math is right) but less salts (about a quarter as much) but would still be better than water. And water alone would be better than dying.
Some sports drinks do contain close to this amount of electrolytes, particularly those aimed at extreme endurance athletes, triathletes etc. Of course you can always make your own (whether for athletic use or an unexpected bout of cholera). Here's a recipe from WebMD that uses regular household ingredients. Not suitable for children under 12 though, the sugar level is too high. Drinks such as Pedialyte, aimed at children, have a much lower sugar content. So it's fine for adults to use childrens' oral rehydration therapies but not the other way around.