Fruit flies are attracted to anything that is fermenting and often formerly fermented things (like beer).
They are digging the residual sugars in the beer leftover as residue.
The solutions above will work.
You can also keep a small spray bottle of diluted Star San and spray it up in the nozzle and let it drip out. This will flush out most of it.
Black Pug Brewing
- Progress Thread
In the fermenter:
Pugkin Ale, Apfelwein
In the keezer:
Black Pug Coconut Porter, Black Pug Wheat, Black Pug IPA
Black Pug Blonde Ale