[Steven Morgan]

Dump it. Cut your losses. I just poured a whole keg that got a phenolic infection, probably from airborne yeast.

[Lazy Ant Brewing]

I have a few dead fruit flies in the vodka inside my airlock --they are small enough to get inside the little vent holes in the cap.  I hope none have fallen through the open tube into the fermenting wort.

I wonder if I could put some cotton soaked in vodka into the top of that tube?

Thanks in advance for your advice.

[Robert]

Cotton makes a great barrier on its own, I wouldn't bother soaking it in vodka.  That might just make it a mushy plug.

[KellerBrauer]

I agree. Cotton should be sufficient. As far as any getting past the vodka, highly doubtful. They most likely died on contact with the alcohol.