The subject of this challenge is advertising. Take it wherever you want to go. Write a jingle. Use a classic line of advertising in your song. Sing about an offensive billboard you once saw. Or do something like this. Whatever, you are only limited by your own imagination (kind of like the Green Lantern).
Send your production-free recordings to rocktastica at gmail dot com by fall equinox, just because I am all about the equinox. As always, winner gets to gloat and pick the next challenge.