For a 32oz Nalgene Bottle (the standard biggish one) of clean water, the Oral Rehydration Salt quantities are:
Slightly less than 1/2 teaspoon of Salt (0.43tsp. to be exact)
7.5 teaspoons of Sugar
(Personal note: when you’ve made it correctly, it should taste like minusculey-sweet saliva)
Adapted from Rehydrate.org’s ORS Recipe based on 1 liter of water.
And the wikipedia entry on Oral Rehydration Salts (ORS)