Sometimes a sneeze is just a sneeze. If this sneezing has been going on for long periods of time, then you would need to figure out what is causing this and treat it if you can.
Is she sneezing dry or wet? If it is a dry sneeze, she may have breathed in something dusty for now. Maybe something is just temporarily irritating her breathing passages. If the coop is dusty or the run, this could be causing some sneezing. if the sneezing becomes chronic, you would want to make some changes to their environment
If the sneezing is wet, and has been going on for a long period of time, then you would want to get her on some antibiotics. This sneezing could be contagious and turn into a monster if not taken care of.
Adding apple cider vinegar is always a healthy thing to do for chickens. It won't cure anything, but it can help as a preventative and aid in good health. You would want to mix 1 or 2 tablespoons ACV in one gallon of water, in a plastic only waterer, changed daily and made new if offered for more than one day. You can offer this up once a week for good health.
Good luck with your babies and enjoy BYC!