Could sugar in my urine be a sign of diabetes, if my urine test had sugar in it during my fever and flu visit?

YES. Increased glucose in the blood/urine in a diabetic can represent a "stress response", and may serve as the "canary in the mine" when it comes to infections. If normal glucose levels all the sudden become labile and hard to control, it can precede the signs and symptoms of a bacterial infection by a day or so-.