Flovent, Pulmicort Turbohaler, and Advair Diskus, will all cause oral yeast infections (thrush) if not rinsed out of the mouth. Having the spray or powder sit in mouth suppresses the natural bacteria in the mouth, allowing candida (yeast) to thrive. You should always drink something after taking a puff. I was also told by a doctor that water doesn't even do a great job of getting it out of the mouth and that mouthwash is a better rinse.
I do find that my son starts getting a very odd smelling *bad* breath when he uses Flovent and only the water or a drink to rinse. If he goes and uses his mouthwash, he seems to be rid of that.