Cranberry juice. It is good to prevent UTI esp in women. However, their ability to cure infection is suspect at best. If the infection is mild, you can try it with a close attention to see if not better in a few days then you need antibiotics. Note, if you actually mean kidney infection (pyelonephritis) i.e. Fever or loin pain + UTI I would treat promptly with antibiotics through your doctor.
Pyelonephritis. If you truly have a kidney infection, you will have severe pain and fever and be very ill many pts with this condition need I've antibiotics and a hospital stay..