It stains the mucus membrane, but you can apply it topically to the sores in your mouth. I think its cost about $2.00 Gentian Violet. It is OTC but you have to ask for it. It does not cure but it does help to clear the candidia up for a while. If you have insurance there are prescriptions for yeast infections.
You may want to also try anti-fungals, like cinnamon and oregano extract.
No really recommended, but it helps eating plain yogurt or even apply it external helps treating yeast (candida) infection. Diflucan/Fluconazole is still your best bet.
Plain Yogurt is the super sour tasting one with no sugar. Sugar helps those bacterias to grow, so stay away from the sweet stuff..