make sure the dog has access to fresh clean water .
Not only allow your dog to drink more , give him more opportunity to pee . Holding urine for a prolonged time can contribute to bacterial build up . Generally dogs that have a diet with good raw meat have a more acidic pH , grains shift it to being more alkaline which is a better environment for bacteria to grow. You can add a bit of apple cider vinegar , natural type such as Braggs is good.
Adding some chopped parsley greens , or adding stinging nettle , which you can buy in powdered capsule form , or dandelion greens , which you can buy fresh at your grocer , or as a dandelion tea , will act as a mild diuretic and get the urine and cleansing flowing.
UTI's can be cleared up by giving cranberry powder , whi ch you can buy in pill form , or add unsweetened cranberry into his water . Natural treatment for UTI in dogs and cats The Cranberry Bog
Problem with relying on anti-biotics is that there tend to be rebound effects with different strain having to be dealt with the "next time" or developing anti biotic resistant strains.
If you are adding yogurt , make sure it is plain , unsweetened -- watch out that it does not have any artificial sweetner . Sucralose is a common one !!!! NOT GOOD for dogs . If adding yogurt find the one that has the highest probiotic contribution , which in yogurt is not that much --