It's a promotional bike given away to stores that sell Cruzan Rum. See this link for an example: http://www.internetwines.com/cruzanbikegiveaway.html
I've seen similar bikes for Corona beer and various other brands. Not sure who makes it, but I wouldn't think the quality is that great. Probably equal to huffy.
And u don't think that it would be possible (or worthwhile) to make turn the tub tube into a tank. The bike in the OP's post has its tank underneath the seat.
Hope that helps.