If your enemy is hungry, give him food to eat; if he is thirsty, give him water to drink. In doing this, you will heap burning coals on his head, and the Lord will reward you. — Proverbs 25:21-22
Have some gift cards handy or, pre-pay for x amount of sandwiches, etc.
It will heap coals on their heads.
Better, gift cards for condoms and HIV testing.