to remove soy sauce stains from upholstery:
1. Combine 1 cup of lukewarm water with a bleach- and alkaloid-free crystal detergent (such as dishwasher or laundry soap).
2. Blot this solution into the carpet or upholstery using a clean cloth.
3. Drop 1 tbsp. of ammonia into 1/2 cup water. Using a different clean cloth, blot this into the carpet or upholstery on top of the detergent solution.
4. Apply the detergent solution a second time, on top of the ammonia.
5. Get a sponge and some clean water. Soak the sponge, wring it out and blot the soy sauce stains in your carpet.
6. Supplement your efforts by applying a carpet cleaner spray product to the stain, as per the instructions on the label. Consult a professional carpet cleaner if you still cannot remove the soy sauce stains.