Is it possible to get sponsored to drive cross country for a charitable cause or for advertising for a company?

Me and a buddy of mine have been dreaming of driving cross country for the longest time but have never been able to finance it. We will do anything to make this dream a reality and would love to incorporate either a charitable cause or worthy advertising campaign for a company to make this happen. Are we just dreaming or can you actually get sponsored to drive cross country? I hope we're not crazy.