Of the ones I’ve had experience with, I would recommend all the iota-carageenan based sprays: Betadine, Luca V-defense, Flo Travel Spray. What little studies they’ve done have shown at least some effectiveness. It coats your nasal passage with a thin film of carageenan which is derived from seaweed and traps small particles like dust and virus. Super-snot, basically. Doesn’t irritate the nose like other sprays do.

I’ve also seen generic saline sprays with iota-carrageenan added, which should basically do the same thing.

Covixyl has done animal studies that showed effectiveness, but it stings which some people don’t like. I used this a lot unti they added an xylitol that irritated my nose and made it start running for an hour.

Xylitol based sprays supposedly work, but it bothers my nose so I can’t vouch for them. The main brand is called Xclear. They are easy to find. Supposedly changes the ph of your nose to make it hostile to viruses. Didn’t work for my friend who used it when their partner was sick, but that might just be a limitation of nasal sprays generally.

There’s also nitric oxide sprays, but the main developer of those types of sprays (Enovid) is based in Israel and it’s not authorized for distribution in the US so you have to import it.

There were also some evidence that the ingredient in neosporin can trigger an immune response and fight of viruses that way, with some people suggesting you take a q-tip and apply a little bit to the inside of your nose when going someplace high risk, like taking a flight or whatever. But that’s anti-bacterial and probably not a good idea to do too often. If you are doing something particularly high risk, like a concert in a crowded bar or something, I would do the q-tip thing on top of a nasal spray.

But if you are exposed to a lot of virus in the air for a long duration, these probably won’t be enough to prevent infection, but reducing the amount of virus you are exposed to is a good thing.