Hefeweizen (one F) is the only correct spelling. Therefore, I don't think the domain is worth anything. I see it was registered in 2007, so I guess your total cost so far is ~$20-30. Assuming no considerable traffic, I think it's unlikely you will be able to sell it for that much, at least if the buyer knows the correct spelling. You should probably let it drop if you can't sell it by next year.