What is the reaction when carbonated drink go bad?

When describing a beverage that has gone bad, the drink goes ‘flat’ which means it loses its effervescence and has become stale. As far as a specific chemical reaction name for this, I have no idea.

The carbonation in carbonated drinks is caused by carbon dioxide which is dissolved into the water. It only remains dissolved in the water under pressure though, which means when the seal remains unopened. When the seal is opened and some drink is poured out, there is now air for the carbon dioxide to escape to, and this is why your drink becomes flat over time when it’s been opened once but sealed back up. The wikipedia article has more information including the exact formula for effervescence.

H2CO3 => H2O + CO2

Typically, my reaction is to make a yucky face and pour it down the drain.

^^^Exactly. If I don’t see bubbles when I pour soda into a cup, I pour it into the sink. Sometimes I’m brave enough to take a sip just in case I’m wrong.

I’ve been told that adding some club soda to a “flat” soda will return fizziness to your now dull soda. I have not tried this yet. Although I just might need to, since I now have some flat soda…

My personal reaction? BLEGKH! :P.