Fish sauce and red wine, apparently.
Garum et vinum rubrum Marcus bibit.
Fish sauce, definitely.
How would you ask "What is Marcus drinking?"
The same, Quid bibit Marcus?, as far as I know.
As of yesterday it was not accepted. I reported it.
I was tempted to try "Marcus drinks what?"
If Marcus is the guy who came up with the phrase, "Ego non sum ovum," then asking what he drinks is indeed an excellent question.