Sounds like they were gargling and rinsing sinuses with it. I didn’t even know you could do that.
Probably used a Neti pot.
Another home remedy I learned about is sniffing a "salt pot" with a few drops of 15% iodine. 15% is hard to find, but you can get it directly from Lugol's. It burns too, and will make you cough. I heard this from a British doctor online who said that salt pots are good for asthmatics..
All I know is I haven't caught the 'rona.