I don't know about 'winning' a cruise but if you're hankering for one, there are some really cheap ways to go. Especially if you're impervious to the blandishments of the staff as to onboard drinks (expensive), onshore dinners and tours (expensive) onboard laundry service (expensive)... The charges for those things bear no resemblance to the cost of providing it. If you resist them you're home free, so to speak.

If you are willing to travel in Alaska in June, especially early in the month, or in late August and in September some 7-day cruises are available for $600 a pop. I've been told of even less.

You have to get yourself to the embarkation point, of course. Most of these cruises originate in Seattle Washington, or in Vancouver BC.

Alaska is still a kind of specialized destination. I would imagine that you'd find the equivalent or better in trips to the Caribbean.