The most important thing to know about drink packages is that most cruise lines require every adult in the cabin to buy the same package. If one person wants the package, everyone 21 and over in that cabin has to buy it, and kids usually need the matching soda or non-alcoholic package.
Whether a package is worth it depends on your itinerary. On port-heavy cruises (most European sailings), you’re off the ship most days and it’s hard to drink enough to break even. On a Caribbean cruise with several sea days, it’s much easier to get your money’s worth.
Package prices change often and vary by line, ship, and when you buy, and many lines discount them before sailing. Do the math: compare the daily package price with what you’d normally drink, including bottled water, specialty coffee, and soda. Packages are bought directly from the cruise line after your booking is created.