Disclosure: Some links are sponsored. If you try a sponsored app, such as Speaker Cleaner: Eject Water, we may earn a commission.
The idea
A low tone makes the speaker cone vibrate strongly, which pushes droplets out of the grille.
Evidence
Apple uses the same principle in Apple Watch Water Lock. It helps with the speaker grille but won't dry the inside of the phone.
How to try it
Use a speaker-cleaner app such as Speaker Cleaner: Eject Water or a tone video, at moderate volume for short bursts.