The severity of the yeast infection, your body's natural defense, and the type of yeast that you have really all affect how quickly your yeast infection will go away. Some yeast infections tend to stay, linger and come back over and over, while other's will go away with a few treatments.
I personally believe that the fastest way to get rid of a yeast infection is by going to the doctor and getting prescription antifungals. They will most likely get rid of a yeast infection faster than any other method. Your doctor will most likely prescribe a cream first, and may or may not depending on the severity give you an oral antifungal like diflucan, which is extremely potent but does the job.
If you wish to go a bit natural it requires a bit more work, but will ensure your bodies immune system is strong enough to fight off the yeast infection. I do believe even if you take your prescription antifungals, you should combine the two of them, and staying healthy really wouldn't be harmful to you. You should consider eating a diet geared specifically towards treating Candida, meaning staying away from grains, sugars, alcohol, preservatives and trying to eat naturally and healthy. You can take apply certain antifungals like tea tree oil (do not apply pure tea tree oil to your vaginal area), and take apple cider vinegar. If you want you can take probiotics and antifungal pills as well, they will crtainly help any candida infection.