The sugar is important because it helps the stomach absorb water faster. Especially if you are treating diarrhea, or other severe dehydration, you need the water in your system fast.

Homemade formulas are the cheapest and work just as well.

Steps for Sugar Salt Solution
1. Always wash your hands first.
2. Fill a cup with 250-300ml of water.
3. Add a two-finger pinch of salt to a clean glass of the safest water you have available.
about .60ml. salt to 250-300ml. of water.
4. Taste the drink. If it is saltier than your tears, throw it out and start over. Too much salt is dangerous.
5. Add a palm of sugar – no bigger than your thumb. about 5ml. to salty water.
6. Mix until you cannot see the salt and sugar anymore.
7. Drink slowly. Finish the whole cup or glass.
8. Make and drink another glass after each runny stool.

https://lifewater.org/wp-content/uploads/2018/10/Lifewater-WASHinSchools-Manual.pdf