It is not David Blaines trick, it is a trick he uses. There are quite a lot of stuff about this effect here, you should do a search for them.
You can use any can, some are better than others, but any can can be used.
Of course it's impossible, that's why it's magic!
I've only used this once, for my audition for my magic circle, after that it has sat in my cupboard, but it is a good trick given the right circumstances.
I would have a carefull think before buying this trick, it requires a fair bit of preperation and is a bit messy. If you haven't already seen it, there's a demo at
www.magicbox.uk.com .
I'm not a big fan of this trick but as I said , given the right circumstances it could look like a miracle.