Does Coca-Cola go off

Answer 1

When coca cola goes off, it gets an unpleasant flavour, a bit like bad cherry flavour. this gets worse the longer it is exposed to warmth.

I'm guessing it's a chemical reaction made faster with heat.

many shops sell this off coke, and many people don't recognise the flavour unless both the good coke and bad coke are available for side by side comparison.

good coke has a sweet pure flavour, off coke loses some of this sweetness to an unpleasant, almost bitter flavour. this effect becomes stronger over time.

if you have an old, empty bottle of coke sealed somewhere, it will probably smell of the off coke if you open it and smell. the high sugar content reduces the likelihood that mould or fungus will grow in it

at some point i intend to have both good coke and bad coke chemically analysed to work out what the problem is.

Coca-Cola has an address you can complain on, but i think you need to call them to get it.