Electrolyte Replacement

Isostar, Gatorade, any good sports drink should do it. On shall only drink to compensate the loss. I generally need around 0.5 liters every half hour, but if the weather is hot and humid I may need almost twice as much. I generally take some Isostar or Inkospor Endurance before the workout, and then take a good gulp every ten minutes or so. At such rate I drink around 1L per hour.

For prolonged effort over 2 hours, and therefore more liquids, I may add a salt tablet for good measure.

Rides up to an hour, usually just water, no gels or anything.  Running, which is harder for me, I start taking some sort of electrolyte replacement for anything over 1/2 hour.

Rides longer than that - I usually take an Endurolyte before and then some mixture of sports drink/gels/solid food.  I might also take more Endurolytes during the ride.  I have found that for me it is really important to replace the electrolytes I'm losing in fairly heavy doses.  But then again, after exercise, you could mistake me for a human salt lick.  My skin is saltier after working out than it is after jumping into the ocean.  Before I figured this out I used to get stomach cramps, and also sometimes I would feel dizzy and chilled (even if the day was really hot and humid) and I would have problems with getting enough liquid. Now I don't have any issues. 

Right now I use Crank Sports e-gel, and e-fuel which have a lot of electrolyte replacement in them, and which are working really well for me.  It might be too much for you though, it really depends on not only how much you sweat, but how much salt you're losing.  You might find that you crave really salty foods after working out, that is usually a sign that your body is trying to replace the salt you lost.  I usually want to eat dill pickles after a long ride, and I can taste the salt in other products where I usually can't.

What sports drink/gel combo will work best for you is a really individual thing, try a few products out and see what tastes the best/gives you the best energy.  Gatorade is a good place to start, it works for a lot of people.

That sounds like they gave you "Oral Rehydration Salts". Did it say "World Health Organization" on the packet? They're used for treating cholera patients and the like in developing countries. They taste terrible, unless you are profoundly dehydrated. They are very effective, however.