I am by no means a Latin expert, but from what I understand in my study of other languages (not on Duolingo...my scores don't accurately represent my language ability!), using "you" to describe a general rule (I believe known as the proverbial you, but I could be wrong) is exclusive to English. Likewise, this is not a command, but a statement. If it were a command, it would be something like "Noli garum beber."
Okay, someone didn't listen. TastingHistory not only MAKES Garum, he also drinks it - and there's a callout to this question on this course! "I finally made GARUM | Ancient Rome's favorite condiment" - https://www.youtube.com/watch?v=5S7Bb0Qg-oE&fbclid=IwAR22dSZ6dtHhxHZMRCoKlYEsOh7yJfB0nsw3eMoHr0i0tOFcc9jYdf6SqXw&feature=youtu.be&app=desktop Be warned that I intended to only watch this one video, and have now had his channel playing for 40 minutes, because it's interesting.