The most likely culprit is a UTI. Like humans, they can clear up on their own, but often require antibiotics to resolve. If the hematuria has continued, or if your dog is showing any other signs of illness (lethargy, incontinence, accidents, or dribbling urine, pain, nausea, irritability, fever, etc), I'd probably request a urinalysis. It's cheap and easy and will put your mind at ease. Depending on your vet, they may not even require a visit if you just bring in the sample for them. Even if you aren't still seeing any visible symptoms, it wouldn't hurt, since dogs can be very good at hiding illness.
Cranberry juice (not from concentrate, no sugar added) can be beneficial to dogs with a UTI, but since it is bitter you're unlikely to get your dog to drink it easily. The purpose is just to change the acidity of his urine so that the bacteria is more attracted to the liquid than to the bladder wall and thus can be flushed out more easily. Vitamin C supplementation is a more direct way to do the same and is considered safe for dogs (at least in the short term), but you'd want to check with your vet to get a safe dosage for your dog since you're dealing with a much higher concentration than you'd get from the juice.