First off, try to keep a change of shirts somewhere on the job along with a wash rag and towel. If you can't manage that, then you're going to have to carry an extra shirt with you everyday. Get to work 15 minutes early everday. Wash up and change shirts. Make certain that you have deodorant with you. You'll need a comb, too.

Don't do anything out of the ordinary, like hang your shirt up to dry somewhere or something. Don't do anything that can be interpreted as unusual. This is a new job and you want to appear as normal as possible...