Jeff Duntemann has a really nice how-to on building a Wi-Fi waveguide antenna from a “Tetra Brik” type container (the kind of foil-lined packaging that Swanson Chicken Broth and Kitchen Basics Beef Stock comes in). I like the first part of this intro:
A lot more has been said than written about the legendary Pringle’s Can Wi-Fi antenna, and a lot more people have talked glowingly about them without ever actually using one. Look closely, and you’ll see that you have to add various things to it to make it work even so-so. Unless you have a can with a foil lining (not all Pringle’s cans that I’ve seen do) and unless you can make good electrical contact to that foil lining (not a slam-dunk, trust me!) the can won’t act as a waveguide antenna and thus won’t throw your signal very far or bring in anything from a distance… Don’t obsess on the Pringle’s solution. There’s an easier kitchen-trash antenna to be had: The Tetra Brik Soup Box.