Sugar in my dogs urine?

I took my dog to the vet today with a urine sample because I thought she had a urinary tract infection. They tested her urine, and it came back with sugar in it. We done a diabetes test a few days before and it came back normal. Has anyone else had this experience with their dog? Does anyone know what it could possibly be? My veterinarian is keeping her over night to run some blood tests and make sure all of her organs are working properly. Any information on this is greatly appreciated. I'm very worried about my baby girl...