What is the Perfect Way to Spend a Dollar?

On our way to Sunday morning tai chi class, we pass several traffic lights where there are always one or two homeless people hanging out with signs asking for handouts.  I always turn to John and ask hm to give me money to give them.

"They're only going to spend it on booze or drugs.  I never give beggars money.  I grew up in New York, you never do that in New York."  John mumbles as he begrudgingly hands me a dollar bill or points me to the ashtray where we keep our parking meter quarters.  This has become the ritual exchange that we have whenever I want to give money to a homeless person.

I agree with John that there is a high probability that the money we give will be spent on more booze or drugs.  I have given this some thought.  In the Buddhist view of the world, an opportunity to give to someone in need is an opportunity to rack up auspiciousness in our lives.  It's a gift that the homeless person gives us that invites us to be better, more compassionate people.

I don't really buy into beliefs that giving anything to others gets us into Heaven any easier or keeps us from being reincarnated into snakes or worms.  On the other hand, from a philosophical perspective, we are all a part of the same universe.  The idea that "this is my money, I earned it, and you can't have it" somehow implies some sort of greedy attitude that says "I value money tremendously, and as such, I think I'm a better, more valuable person than you are because I have this money and you don't, and neither do you deserve it."  I might be over-exaggerating the fictitious dialog here, but my point is, does it matter exactly how that dollar is used by the person that I give it to?

If I hold a dollar bill in my hand and ask myself "how can I best use this dollar bill?", then how would I want to spend it?  Stick it in my pocket for lunch money?  Invest it in the stock market?  Save it for a rainy day?  Add it to money to buy something cool?  Take a homeless person to the local McDonalds and buy them a hamburger?  Send it to the "Free Tibet" fund to support peace on earth?  What exactly defines the absolutely most perfect way to spend that dollar bill?