Once you have opened that can or bottle keeping it carbonated can be a challenge. This guide is about keeping soda fresh.
Always store 2 litre bottles of soda, once opened, on their sides in the fridge. As long as there is enough soda in the bottle to cover the cap, the soda will keep its fizz.
By Jo from Riverside, RI
I haven't tried your idea but squeezing the bottle a bit before putting the cap back on and standing upright works too :-)
It might be done by everyone, I don't know, but I thought it was a simple but good idea!
By AHA! from NE Pa
To keep canned soda after opening, place a small piece of plastic wrap on the can with an elastic band. It's just like a top.
Instead of throwing away half a can of soda or leaving it to become decarbonized, place a balled up piece of foil in the drinking hole sealing off the majority, if not all, of the can. Place it in the fridge. Two days later, your soda still has that satisfying "fizz". Thanks to Grandma.