Despite his hunger, how does Bakha end up too nauseated to eat the food his brother brings home?

Bakha eats a small amount, but as he repositions himself, his hand contacts a piece of wet bread. He knows immediately what has happened: the bread is the scraps of some sepoy's meal, and as the man washed his hands over the remains of his meal, the bread got wet. The sepoy then threw what was essentially his garbage into Rakha's basket. Taken on top of everything else that has happened that day, this is too much for Bakha, and he feels too sick to continue eating.