This question comes from Giel M, via rpg.net:
What's the most efficient way to transport large amounts of beer on the back of a bicycle?
That depends on what you mean by "large amounts" and what you mean by "efficient." I am going to assume that you want some combination of maximizing speed and minimizing effort and risk of spillage.
Your method should vary depending on the amount of beer you want to transport. If we're talking about a single twenty-four pack of cans, it would probably be most efficient to remove the cans from the package and place them in a backpack. Depending on how much space was left in the backpack, you might want to fill any empty space with wadded up paper towels to keep the cans from shaking in transit.
For multiple cases, a cargo rack would be best. These are attached to the back of a bicycle, and when properly loaded, will not disrupt your center of balance. Just remember to securely fasten the beer (hint: if you think it's too tight, it's probably not), and to take into account your greater mass and lower agility when navigating.
A cross-section of cargo racks.
If we're talking about a keg, you'll probably have to go with a trailer. These are not too expensive, about 100-200 USD, but I can't attest to how they affect the riding experience.