I have had several UTIs in the past and have had to treat them all with antibiotics since the infection goes downhill fast for me from the onset.
However, a couple of months ago I recognised the onset of the infection and felt helpless inside, that is until I drank a cup of green tea. I'm hoping this is what prevented the UTI getting worse because the symptoms vanished hours later, and it is the first time it's gone away by itself. So I recommend some green tea maybe. Cranberry juice is the popularly advised drink though.