Your best option is to bring a change of clothes with you onboard including 2 face cloths. A few hours before they serve breakfast get up make your way to the washroom. I usually wash my body with a damp washcloth with some soap and the dry myself with the other washcloth. I shave and ash my face etc.

Then change your clothes into fresh ones. Voila you have a fresh you, I have done this many a times except when I am transiting then I wait for the lounge.