These are supposed to be quite effective:

Nasal spray: 2-3 times a day A 1% povidone-iodine nasal spray and a nasal spray with Iota-Carrageenan are potent inhibitors of SARS-CoV-2 and influenza virus, and dramatically alter the course of infections with these viruses. Nasal irrigations with saline as well as neutral electrolyzed water may also be of some benefit.

Mouthwash: 2-3 times daily Antiseptic-antimicrobial mouthwashes have been shown to inhibit replication of multiple respiratory viruses, including influenza and RSV. We recommend products containing chlorhexidine, povidone-iodine, cetylpyridinium chloride (e.g., Scope™, Act™, Crest™, or the combination of eucalyptus, menthol, and thymol (e.g., Listerine™).

There's other items in the protocol, check them out: https://covid19criticalcare.com/protocol/flu-rsv-treatment/

The organization that puts out this information (FLCCC alliance) were very good during covid in providing treatment protocols, I really respect them.