There have been studies on some probiotics helping with
recurrent bladder infections. Yogurt also has this benefit.

Females get bladder infections when they overdo the hygiene issue, and wash away protective compounds. Thong type underwear has been suspected to spread bacteria to the bladder as well.

It is best to wash down there lightly, and use a pH neutral soap like baby shampoo. Soap residues "down there" burn and can irritate and open the way to urinary infections. Bubble bath salts are known bladder infection triggers for the same reason.
Women with infections that recur should NEVER use bubble bath salts or soak water softeners.

Cranberry extract is very good...it prevents bacteria from sticking to the wall of the bladder, and prevents infection that way. Taken in capsule form, there is less sugar to deal with too.