How do you make soda flat, instantly??

If it were me, I'd put some soda in my mouth for the taste, then spit it out in the sink. Gross, I know....but if I wanted the taste I'd do that just to get it over with. To get the soda flat I'd get it in a bottle and keep shaking it, letting out the fiz by slowly opening the cap and repeat until the fizz is gone.

I have done that with a few carbonated beverages that I didn't realize were carbonated when I took the sip.  Once I swallowed a little bit before I realized... then had to spit the rest into a napkin.  I have been really good about not getting carbonated beverages though.... but I confess, it sure tasted good and felt good in my mouth.  ;o)

A wooden stick works best (wooden spoon, chopsticks)

Probably the fastest/best way is just to pour it into a large tall glass and then stir it with a long spoon (some say a fork) ..  Stir rapidly and let it stop fizzing ..  Do this several times until you can get as much fizz out as possible ..  Some folk say pouring it ove ice also helps speed the process ..   If I know I'm going to enjoy a soda later in the day, or in the next a.m., I open a can and leave it open in the fridge ..  It  is usually flat within a few hours ..  If i bring home a 2 litre bottle, the first thing I do is open it to let the gas out of it (initially) .. That makes it easier to defizz later after pouring ..