I thoroughly dislike to drink beverages supposed to be sparkling once they have become still.
Apparently there's no definitive solution to this.
Inevitabily the bottle will be moved (repeatedly) while still in use, and the beverage inside is therefore inevitabily going to flatten at some point.
However I've got the feeling that something to improve the situation might be done regardless.
There's an urban legend around according to which a beverage stored in a bottle will keep its fizziness the best by not closing the bottle with a top and by putting a spoon from the side of the handle inside the bottle neck. Tested it and it doesn't work, or at least the results are not really satisfactory.
How can I keep sparkling beverages the fizziest as possible?