If you're not using the mark in commerce. If this is just an idea -- that is, you've come up with a good choice for a name and you don't plan on manufacturing and selling the drink -- then you don't really have any trademark rights to sell. Trademark rights are derived from use of the mark in commerce (or to some extent a bona fide intent to use the mark in commerce). If all you have is an idea, then you have no proprietary rights and once you post the name for sale, anyone can use it. (And the first company to use it -- assuming the trademark is distinctive-- will acquire trademark rights.)
If you are using the mark in commerce. If you are using the mark in commerce, and hopefully you've registered the trademark, then you can sell or auction it anywhere that permits such a sale. Ebay policy doesn't expressly prohibit the sale of trademarks, so we assume eBay permits it. And there's at least one eBay store that seems to specialize in the sale of trademarks and domains. And of course, there are various intellectual property auction sites where you can sell trademark rights. The Dear Rich Staff has had no experience with these sites so we can't vouch for any of them.
The domain names would be a different story. The domain names may have value whether you are selling the product or not. And because you control the ownership via a domain name service, selling domains is easy. As you're probably aware, there are many sites such as afternic and great domains, where you can sell your domain.
What's your trademark worth? Short answer: you'll find out when you try and sell it. Long answer: you can hire a professional IP valuation team to give you an opinion -- a procedure that may cost you more than your mark is worth. Here are some of the gruesome details.
