Sorry I just saw this. How is cat doing? Upper Respiratory Infections are not uncommon in cats and kittens, and like colds in humans are easily spread when around others (as in shelter or foster with a number of cats)). Otherwise healthy adult cats can usually recover fairly easily. Being in a home with fresh air and room for activity helps. However kittens and seniors have a harder time. At this point if sneezing hasn't cleared up, see a vet. Sneezing could be from dust as in litter or dry air. (humidifier helps cat as well as family). But warning signs of need for vet visit is , mucusy sneezes, runny eyes, fever or unusually low temperature (cat's normal temp is about 101). If cat is unusually lethargic or isn't eating or drinking water etc,
There a various medications vet can prescribed depending on cause (bacterial or viral)
Hope your cat is better by now.