I just stick with water.
Once you start adding sugar to stuff it can grow bacteria and yeasts more easily. A trace amount of salt may be useful, but if you are eating food, you are getting the electrolytes you need. I once heard that diluted Coke (not Pepsi) could be used as a rehydration fluid. Coke has sugar, sodium, and potassium. The sugar helps your body absorb water more quickly, so that could be useful if you are severely dehydrated.
Consuming excessive salt can lead to the loss of fluid. A prime example is sea water: drinking salty water from the ocean will cause you to become dehydrated as your kidneys try to excrete the excess sodium. Delirious sailors lost at sea have proven this on a few occasions, much to their detriment.
Stick with water. You've evolved over 2 million years to drink water successfully. Why mess with that?