To keep a soda from going flat, you want to keep CO2
O
2
(the gas) in solution and in the bottle. By squeezing the bottle, you will be expelling the gas from the bottle and leaving a lower pressure in the bottle after the cap is replaced. Both actions will disturb the equilibrium and cause more gas to come out of solution as the bottle returns to its normal shape. (Come to think of it, if you squeeze with a clamp which maintains the squeeze, that should help.) It is better to open a bottle which is cold. The pressure will be lower inside and less gas will escape. An ideal dispenser takes fluid from the bottle without letting any gas escape, but more empty space in the bottle lets more gas come out of solution.