Whenever I say that there are some sweepstakes that you don't want to enter, there is always someone who insists that entering every sweepstakes is the way to go. Not true. In general terms, there are two types of sweepstakes that you don't want to enter 1) sweepstakes for which you are not eligible, and 2) sweepstakes where the prize would not benefit you.
The first one is more obvious. If the Rules let you know that they are only accepting entrants from certain states, within a certain age group, or in a particular category (smokers, teachers, small business owners, etc…), don't enter if you aren't in that group. The sponsor is not obligated to give you the prize if you don't meet the terms of their sweepstakes.
I will give you an example of a prize that it would not benefit me to win: a speedboat. I don't live on or near the water and couldn't use the prize. I don't want to pay taxes on a prize this large. Sure, I could sell it, but if I have to pay marina fees, transfer fees, and who knows what other kind of fees, this could get pretty pricey. There is also no guarantee that it would be easy to sell a prize like this either. If it took me months to find a buyer, I could actually end up losing money on this prize.
My point is, think before you enter. If you want the prize to keep, gift or sell – go for it. If not, leave that sweepstakes for someone else.