Champagne and Sparkling wines will loose the effervescence
The best thing to do is to drink it, but if you feel that you will not be able to finish the bottle within an hour or so. Have a “champagne stopper” readily available and place the bottle in the fridge or on ice. This is the best way to preserve the effervescence. In my opinion, even with a stopper, the wine will go flat in a 24 hour period.