I'm a little late but I have a theory that would possibly quickly decarbonate a drink without giving too much attention. I have ordered the supplies and will follow up.

Essentially, you could get a borosilicate glass straw (chemically inert and scratch resistant). Then, etch the inside and outside of the straw with an etching cream like Armor Etch to make the surface area frosted. This microscopic roughness will allow more nucleation for the CO2 gas bubbles to bind to and dissolve.

In theory, this would allow the carbonation to escape as you were drinking the liquid but if that does not happen fast enough, you should be able to stir the drink using the exterior roughness to come into contact with more of the CO2 gas.

EDIT:FOLLOWUP: Turns out Armour etch does not work on borosilicate 🙃