Rehydration is the replenishment of water and electrolytes lost through dehydration. It can take place by mouth (oral rehydration) or by adding fluid and electrolytes directly into the blood stream (intravenous rehydration).

If no balanced oral rehydration solution (commercial preparation) is available, a simple solution of salt and sugar in water may be used:

1. level teaspoon of salt (no more)

2. 8 level teaspoons of sugar (no more)

3. Dissolved in 1L boiled and cooled or safe drinking water (no less)

Reference:
SAMF 7th Edition
http://rehydrate.org/rehydration