The first thing that you should do when faced with a soda on your upholstery is to blot up, dab up and soak up as much of the excess liquid that is possible.
If the stain is already dried, wetting the carbonated stained area with a spray of water is going to take you to the step listed above.
No matter if the soda is dried or fresh, spraying with water, blotting and dabbing up the moisture is going to bring out more if not all of the stain.
Keep doing this as long as you see the soda stain coming out and onto your towel or rag.
If you find that the stain is a bit stubborn, adding a few drops of clear, bleach free liquid detergent to your water and then spraying and blotting up the moisture, you are going to bring up even more of the soda stain.
Rinsing the stained area with just water, getting out all of the suds in the upholstery is important, as detergents will attract more dirt when it is left in the upholstery.
After you have rinsed the upholstery well, you can also rinse with a half and half water and clear white vinegar mixture. Spray this lightly on the stained area and blot, and dab until the upholstery is almost dry to the touch. This ensures that all of your stain and the detergent are removed from the upholstery.
Blot the upholstery well so that you are left with barely any moisture left in the fabric.