Oral rehydration salts

Oral rehydration salts or oral rehydration solution or ORS or oral rehydration therapy or ORT is a combination of electrolytes, usually combined with glucose sugar and a base that, when mixed with drinking water, are typically used to treat or avoid dehydration and metabolic acidosis, especially when caused by diarrhea from infectious illness. It is a more practical alternative to IV saline.

Evidence
Widespread evidence since the 1970s has led to ORS being the standard treatment for acute diarrhea, with a large reduction in deaths of under 5s especially in the developing world.

A 2019 study showed evidence of ORS as an effective treatment of orthostatic intolerance in children.

Costs and availability
Very widely available and inexpensive. Homemade solutions can be made easily.