Oh, come on. I don't care how healthy your diet is; everyone is going to catch a bug occasionally and will need antibiotics. If I'm on antibiotics, I always eat yogurt, and this helps me keep from getting diarrhea from their effects, but it doesn't stop the yeast infection. As a result, my doctor just gives me a prescription for Diflucan when I get the antibiotics filled.
Fact is, the only time I ever get a yeast infection is when I'm taking antibiotics, so cutting sugar and yeast completely from my diet will probably not do any good.
I advocate eating a healthy diet, along with exercise, but that doesn't prevent or cure everything.