What can be done to naturally go up a cup size in a few months?

Only surgery: The only proven reliable method that is permanent is surgery - either with implants or fat transfer. There are no creams, pills, exercises or other methods that have been proven to work.

Natural enhancement: The only known natural nonsurgical enhancement for larger breasts is weight gain however even with large amounts of weight gain, some women's breasts do not change. It is not recommended to try to increase the size of your breasts by gaining weight. Patient should maintain an ideal weight regardless of breast size.