Cyanide

Or bottled water.

Deeper gargle if you can't "taste" the water (eg salt water). Your brain will stronger defend your airway (unconscious reflexes) the more intense the sensation of stuff in your throat (all jokes aside).

You want to wash the mucosa with water so that you can spit out any viral particles that land on the lining of the upper airways, before the virus has a chance to penetrate the tissue.