I am working on a beer related website, and I would like to build a portable light box that I can take to a beer shop and photograph as many individual beer bottles as possible. What is the best way to construct this to ensure proper lighting and the ability to rapidly swap out beers and snap photos?
There are plenty of light tents on the market that would suit your needs:
If you want to go the DIY route, your best bet is to choose a decent piece of diffusion material (thin plastic / acrylic are good for this) and make a tall three sided pyramid and fire the flash through the diffusion material for even lighting, see:
This setup really favours shooting from above however you could build a two sided box with sides at right angles which would give you the ability to quickly swap out bottles. When shooting glass you want the lit-up diffusion material to make up as much of the space around the bottle as possible so you don't get odd reflections of your light tent in the glass.
Unless you are on really good terms with your beer shop, I would have thought they would have frowned on you photographing dozens of beer bottles in their store without paying for them. Why not take the bottles home and use a non-portable setup? If you are on really good terms with your beer shop that they may be happy with you returning them (rather than cluttering up their store for hours). If not then how about buying the beer you want to photograph. Bonus - you get to drink the beer!
There is this tutorial on digital-photography-school how to make a DIY light tent from a cardboard box.
You could in theory scale this down to bear bottle size or make one on site.