What a drip does that a bottle of water cannot
An intravenous drip is a bypass. When you drink water, it has to pass through your stomach and small intestine before it reaches your bloodstream, and that route has a speed limit — roughly a litre an hour under good conditions, much less if you are nauseous or vomiting. An IV skips the queue entirely: fluid goes straight into a vein, so absorption is effectively 100 per cent and immediate. That is the entire trick. There is no exotic technology involved, just a sterile bag of fluid, a length of tubing, a small plastic cannula, and gravity or a flow regulator.
The fluid itself matters more than most marketing admits. The workhorse is 0.9 per cent sodium chloride — normal saline — which is mixed to roughly match the osmolality of your blood, meaning it neither pulls water out of your cells nor floods them. Some providers use lactated Ringer's or Hartmann's solution instead, which adds potassium, calcium and lactate in proportions closer to plasma. Everything else on the menu — vitamin cocktails, glutathione, NAD+ — is an additive dissolved into one of these carrier fluids.