system
Given the following post, respond as if you're commenting on Reddit:
human
If I can increase the air pressure in an opened 2 liter bottle of soda would that prevent it from going flat?

No matter how tight I screw on the cap of a 2 liter bottle, once it is opened it goes flat within a day or two.  My assumption is that because the bottle is no longer pressurized the CO2 has room to escape into the air that is in the bottle.  If I had a special cap that allowed me to pump air into the bottle would that be enough to keep the CO2 trapped in the soda? If so would it all escape as soon as I opened the bottle, or would it work to keep the soda from going flat?
gpt
Here's a thought:  If you put a carefully calibrated piece of dry ice (solid CO2) into the soda bottle before you closed it, you could raise the pressure in the bottle enough to re-fizz your soda.

Of course, if you put too much, the bottle will explode.