The soft drink package is available on all cruises. It is $6 per day plus 15% gratuity.
They offer the popular American beers (Bud, Miller, Coors), Corona, Amstel, Heineken, Red Stripe, Bass Ale, Stella Artois, and Samuel Adams. This is from a bar menu I recently saw. RCI also has "Royal Belgian Ale" which is a brand brewed exclusively for RCI.
Prices range from around $3.50 to $4.50 (also need to add 15%). Note that they sell Bud, Bud Light, Bud Select, and Michelob Ultra in the 16 ounce aluminum bottles and those are $4.50.