I've used the diluted povidon-iodine solution (Betadine) with great success for myself. Not as a spray but as a gargle and nasal rinse with a neti pot. This was during the delta wave and I had a sore throat and 39.5C fever. The rinsing pricked in a good way for a few minutes and then subsided, at which point all viruses seem to be quite dead. Next morning I was completely better.

I do this for the the flu as well. It starts in the nose and throat and if treated early it won't make it's way down into the lungs.