Didn't notice this until today..... Hoping you've talked to your vet?? Sneezing is most likely an allergy or a virus (like the cold virus in humans), and either way, the antibiotic will not do any good. I would think it might be that they caught a virus while at the vet. If all you're seeing is mild respiratory problems (sneezing, runny nose), you're probably ok to just wait it out until it gets better. Just watch out for vomiting/diahrea, lethargy, etc., as these could be symptoms of a larger problem.