Hello Hutch,
The following is a cut and paste from the Princess official policy on alcohol:
Alcohol purchased at any port of call, including the port of embarkation, may not be consumed onboard. It will be collected at the gangway for safekeeping and delivered to your stateroom on the last day of your cruise, prior to your disembarkation. You may bring wine or champagne onboard to celebrate special occasions (limit: one bottle per person). If consumed in the dining rooms or alternative restaurants, each bottle will be subject to a $15 corkage fee*.
(Would burbon that be concidered a wine or just alcohol? =huh)
About the Cola, that is defintely a charged item, not free. Whether you can bring your own onboard, I couldn't find an official policy on that. The only mention of soft drinks I could find on the princess answer page, concerned the availablity of buying a soft drink package, prior to the cruise, apparantly as a gift to the cabin occupants, (like a TA would give to a customer, or you can buy for yourself.)
It wasn't such a great deal if you ask me, offering six sodas for the price of five $10.50. I could have sworn they offered a soft card, where you pay one price for unlimited soft drinks, but I could not find it mentioned. Perhaps some recent Princess cruiser will know more.