Fruit flies would be attracted to the fermented and fermenting bokashi food waste. However, fruit flies will not be attracted to a sealed bokashi bucket, as a sealed bucket is odorless.
The most common problem with fruit flies is in the collection of food scraps (prior to adding to your bokashi bucket). This post may be useful with our top 5 tips for controlling fruit flies. https://bokashiliving.com/top-5-ways-get-rid-fruit-flies/