oopsylon says:
... if Benji wanted to bite someone during a fight it would definitely be turn to violence and then if the situation allowed he could use eternal hunger to actually feed on them (although of course he would have to mark corruption for feeding on an unwilling victim)... Does that sound right to you?
Yes, that is how it might play out. We always look to the fiction first, and in that scenario Turn to Violence might allow you the opportunity to try to feed. You might need to roll a 10+ and make the choice to Take Something From Them or have an Ally Create an Opportunity, but also may be able to arrange things in the fiction so you don't need the 10+.
There are some complications that could arise with such uses of the Moves. For instance, if you rolled a 10+ on Eternal Hunger you get all three of the benefits, which means you
don't do 3 Harm AP... there is no provision in the rules for choosing to not select an option when it is given to you; but also, you Learn a Secret, and that might not be feasible in the middle of a fight (though sometimes it might be), so that option is off the table. Similarly, we could rule that there is not time to be careful and avoid the Harm, taking that option off the table too. We would need to see it in the fiction.
However, remember that the fiction of the situation described is that you are in the middle of a fight and stop to take a drink. There may be consequences for making that in-fiction choice. Feeding is not instantaneous, and you may be vulnerable while doing so. If they are the last foe, then no problems (aside from the Corruption and scaring your companions (which is part of the Corruption)). If there are other foes still active you may first need to set things up such that you can drag your food into an alley to get a moment of quiet to feed, this will put you out of the fight for a short while (sorta 'skip a turn').
It all depends on the fiction of the situation.