Personally, I busk for my money. Some people view busking as begging with an instrument, when in reality it's very different. You're providing a service, and you make money not by how good you are at spinning a sob story or looking pitiful (or, for the ladies, pretty), but directly relative to your skill with your instrument.
I rarely give spangers money, and I never spange (although I would if I absolutely had to). The long and short of it is that if it's food somebody really needs, just about anybody on the streets knows that it's only a matter of finding the right dumpster. Get the right fast food dumpster at the right time, and it's as good as going in and ordering.
Before I even considered spanging, I would be offering a service in return for money. If you have some sort of skill to offer people, offer it. Clean yourself up a bit in a restroom somewhere and go door to door offering to mow lawns, fix cars, do any manual labor they need, whatever you can do. People will be MUCH more receptive to a homeless person who is obviously willing to work than somebody sitting on a street corner with a sign somewhere. I'm not suggesting following this all the way to wage slavery, but if you need money, you'll do better if you're willing to work for it.
I once made $150 from an old man in about three hours by cleaning up his apartment, not to mention he fed me and gave me a place on his floor to sleep. There was also lots of listening to his old hippie stories involved, but I didn't mind that, since they were great stories. When has anybody ever done so well out of spanging?
'course, there's situations where spanging is just plain necessary, but most of the time, there are other ways that'll let you keep at least some measure of your pride.