Stephen Baldwin has a point. Giving food and drink to those in need is a physical manifestation of the Gospel. You are helping those in need, which is essentially what Christ did for us. We have a need for reconciliation with God because of our sin - Christ became that reconciliation for us.
If you give food and drink to those in need but do not also preach to them the Good News of Christ's work of salvation, have you truly helped them in the light of eternity?