Coke used to be mixed, bottled, and shipped out in an extremely quick timeframe. Inventory turned over fast.

I suspect the separated components wind up being equal to what a stale soda has, one that has been on the shelf. It’s like buying a soda whose sugar component has already gone stale.

Sure, the rest of the flavors are there and still fresh, unaffected by the carbonated water, but the sweetness one is off.