Some dogs bark for food during the owner's mealtime. We tend to give food to such dogs because we feel sorry for them, but if we do that, we can not break their barking habit.
If they understand that you will never feed them during mealtime, they won't ask for that.
A good way to do this is to let a dog always wear a lead in a room and pull the lead every time he barks and let him feel uncomfortable. If you repeat pulling the lead at the moment of barking, his excitement will gradually subside and he will not bark.
Also during mealtime, keep letting him wear the lead on, tie the lead to the legs of a table chair, etc., and keep him sitting beside you at all times. Repeat and practice pulling the lead each time he barks until he can be calm and quiet.
It is also effective to keep him in his dog house so that he can not request for food during mealtime.