Ive made a habit of picking up the tab when I see soldiers in the resturaunts. Ive also ordered pizzas for the guys at the local recruiting office several times now. (They're soldiers too)
It's not a huge donation but it just may mean that a soldier gets to buy his kid something special that he couldn't otherwise afford.
It is such a wonderful thing to do. I will have to remember to do the same once I am back in the US. God Bless you.