Yeast is omnipresent, you can brew or brake bread with the yeast on your skin (as seen here [1]). The other part is getting a container and sugars to ferment, see /r/prisonhooch [2] for some creative and horrifying concoctions.

1. https://www.youtube.com/watch?v=PvrJu9dLmtA

2. https://www.reddit.com/r/prisonhooch/