Club soda has long been recommeded as a stain removal method, especially for red wine. Yet, there is no scientific data that proves that club soda gets stains out. In fact, the chemicals in club which are water, carbon dioxide, and a small amount of salt have no properties that would remove stains.
It's in the bubbles
Scientific data is lacking and suggests this is nothing more than an old wives tale. Although, like many wives tales and myths there could be some truth to this stain removal technique. It is theorized that the bubbles are actually key to the trick. Yet, it also depends on how fact the object soiled absorbs stains and how quickly you can return to the stain with the club soda in hand. If a slow absorbing fabric receives a spill and you return quickly enough with the club soda, the soda will act as a carrier to help the absorbency of the paper towels. It is also suggested that the low level of acidity in club soda slows the discoloration process.
Salt works in much the same way. The fabric must have a slow absorbency, and you must return with the salt quickly. Salt works by soaking up the stain before the fabric has been saturated. The white color of the salt will change to the color of the stain, and at this time the salt should be vacuumed up.