Actually there is another way involving Amtrak Guest Rewards. 175,000 Guest Rewards will get you a Premium 7 or 8 Day Cruise with Carnival Cruise Lines.
The AMTRAK card is from Chase and Chase cards can be used to open bank deposits. It would take a massive amount of spend manufacturing but you could generate a free cruise. However, that free cruise would be unlikely to be in a cabin for 4 people.
Originally Posted by
Bored_Russian
The only way I know is Thank You points and Capital One rewards.