I had this same issue and grudgingly followed the vets instructions of switching to royal canin urinary so
I gave it to him along with pills for a couple weeks and when he was back to normal I switched him back to innova (mostly canned) and got some holistic stuff (dont know the name right now) to add to his food to prevent this from happening again. 1 month later, he got it again :sad: So now he is back on the gross food from the vet and it seems to be working, its been months.
I stopped looking for alternatives because I was worried about it returning a third time, and giving him pills twice a day was becoming increasingly dangerous.
I hope you find a better quality food that works for your little guy, I have no clue whats in the food that makes it work becasue the ingredients are pretty gross.
Good luck!
Sarah