Fasting and almsgiving go hand in hand. In the Shepherd of Hermas we read: “that day on which thou fastest thou shalt taste nothing at all but bread and water; and computing the quantity of food which thou art want to eat upon these days, thou shalt lay aside the expense which thou shouldest have made that day, and give it unto the widow, the fatherless, and the poor.”
Fasting “nourishes the poor” says Origen and St. John Chrysostom says unless there was almsgiving connected with your fasting then it’s in vain.
That was fasting according the holy fathers of the Church. What is today? Reading labels and making sure you don’t eat any meat or dairy products.