Ingredients: Water, 9 mg/ml of salt and nothing else
But apparently it's not easy to manufacture; it has to be the right concentration (there are various formulations) and pure (of impurities and germs). Amazingly, the whole US gets its bag of saline from only 3 manufacturers (my observation has been that all of peninsular Malaysia is supplied by Ain Medicare). Apparently Hurricane Maria jeopardized the American supply as manufacturers can't simply ramp it up; interestingly 1 reason for this is the high barrier to entry as the hospital groups' purchasing power ensure that they buy saline at the absolute lowest prices (only the companies with the lowest costs win).
“Oral rehydration therapy has been studied for nearly 60 years. It has been shown to reduce mortality from diarrheal illnesses by 93% and to reduce the case fatality rate of cholera from 30% to 1%. It is less expensive than IV-fluid therapy, and its use results in fewer admissions and shorter lengths of stay. A 2006 meta-analysis showed that oral rehydration was equivalent to the administration of IV fluid for the management of dehydration due to gastroenteritis in children. Data on use in adults have revealed similar efficacy, although in smaller studies. Oral rehydration therapy has been widely adopted in low- and middle-income countries where IV fluids are expensive and resources limited. Conversely, despite this evidence, oral rehydration has not been widely used in adults in high-income countries, probably owing to the widespread availability and ease of use of IV fluids.”
Interestingly, the saline crises has forced American ED's to stop being lazy and do the right thing and encourage oral rehydration. Despite good evidence that it's better than iv fluids (both in terms of efficacy and cost), we still stick to iv fluids for what can only be described as "laziness". There's just nothing easier for the nurses than putting that iv line in, spike that bag of saline, hang it up, and continue with ward work instead of the kind "Western way" of encouraging patients to drink that solution of electrolytes; imagine if it was a typical Asian parent instead of that nurse instead. And if the patient can tell us that the bag of saline has just finished, all the better as now you can simply chart it as 500 ml (or 1 L) in!