I've had great success with soda cans, but I've also had failures. There is nothing quite so frightening as jumping a pothole, only to have the handlebars rotate out from under you when you land. I very nearly almost lost some teeth, or at least some skin.
What I learned? Soda cans work ok, but for a good strong shim, you need
beah
the wider can allows you to make a longer one piece shim, that in my experience has been more durable.