Viral Hack Checked: Flat Cola for an Upset Stomach and Diarrhoea?

Verdict: Waste of time, and risky for children. Flat cola is far too sugary and too low in salt to replace what diarrhoea takes out of you. The extra sugar can pull more water into the gut and make loose motions worse. ORS is the drink that actually does the job.

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Somebody’s stomach turns after a shaadi dinner and, within minutes, someone else is stirring a glass of cola to let the fizz out. “Flat Coke settles the stomach” has travelled from school hostels to family WhatsApp groups and now to short videos with millions of views. Does flat cola help an upset stomach or diarrhoea? It feels comforting, and it’s easy to see why. But what your body needs during dast is water plus the right balance of salt and sugar, and cola gets that balance badly wrong. This is part of our Viral Hacks Checked series.

Why flat cola became the upset stomach fix

The habit is older than social media. Cola was once sold as a tonic, and for decades people in many countries have sipped it flat when they feel queasy. It’s sweet, it’s cold, and when you can’t face food, a few sips of something sugary give a little energy. Letting it go flat takes away the fizz that can make you burp.

There’s also a timing trick. Most stomach bugs and mild food poisoning settle on their own within a day or two. Whatever you happened to drink on day two gets the credit.

What diarrhoea really takes out of your body

Picture your gut as a long tube where water moves in and out all day. During diarrhoea, much more water rushes out than comes back in, and it carries salts with it, mainly sodium and potassium. Those salts help your heart, muscles and brain work. Lose too much water and salt and you get dehydration: thirst, dry mouth, dizziness, dark or little urine, and in children, sunken eyes and drowsiness.

The fix is clever. The gut has a special door that pulls sodium and glucose in together, and water follows them in. ORS is built around that door, with just enough sugar to open it and just enough salt to use it. Too much sugar breaks the system.

Myth: flat cola replaces lost fluids and salts

Cola carries several times more sugar than ORS and very little sodium. When a drink is that sugary, the extra sugar that the gut can’t absorb stays in the tube and draws water towards it, a bit like sugar drawing juice out of cut fruit. That means more water heading out, not less, and looser motions. It also has caffeine, which can make some people pass more urine and adds to the fluid loss.

Letting it go flat changes the bubbles, not the sugar or the salt. The same goes for packaged fruit juice, energy drinks, sports drinks and very sweet sharbat. They taste better than ORS, and that’s exactly why they don’t work as well.

For children this matters most. Small bodies dehydrate faster, and a toddler happily drinking cola may look fine while falling behind on salts. In babies under 1, sugary drinks and fizzy drinks don’t belong in the diet at all.

What to drink instead: ORS, made right

Use a pharmacy ORS sachet and mix it exactly as the pack says, with the full amount of clean water. Too little water makes it too salty, which can be harmful, especially for a child.

If there’s no sachet, the WHO home mix works:

1. Water: 1 litre of clean water, boiled and cooled if you aren’t sure it’s safe.
2. Sugar: 6 level teaspoons.
3. Salt: half a level teaspoon.
4. Mix until dissolved, and taste it: it should be no saltier than tears.
5. Sip: small, frequent sips or spoonfuls, more after each loose motion. If someone vomits, wait 10 minutes and start again, slower.
6. Fresh batch: make a new one every 24 hours.

Keep breastfeeding babies throughout, more often than usual. Children should go back to their normal food as soon as they want it. For adults, plain rice, khichdi, bananas, yoghurt and toast are gentle options once the vomiting stops. Our food poisoning ORS and 24-hour guide goes through a full first day, hour by hour.

For children with diarrhoea, doctors often add zinc for a short course; the doctor or pharmacist decides whether it’s needed and how much, by age. Our piece on loose motions in children, zinc and the teething myth covers that. Don’t give children anti-diarrhoea medicine unless a doctor prescribes it.

Did you know? The oral rehydration idea, a simple mix of salt, sugar and water, is widely credited with saving millions of lives, largely in South Asia, where much of the early work was done.

Dehydration danger signs to watch for

Look for these at every age, and act on them fast in babies and the elderly.

• Very little or no urine for 6 to 8 hours, or very dark urine.
• No tears when crying, a dry mouth, sunken eyes, or a sunken soft spot on a baby’s head.
• Drowsy, floppy, confused or hard to wake.
• Vomiting everything, or green vomit.
• Blood in the stool or black stool.
• Fast breathing, cold hands and feet, or a fast weak pulse.
• Diarrhoea lasting more than 2 to 3 days in an adult, or any diarrhoea in a baby under 6 months.

Flat cola for diarrhoea: common questions