We have one toilet in a old shipping container that has been refurbished inside-there is a small kitchen area and room to hold meetings. A rota was started which includes some Committee members and others from the site- they all volunteered. Those doing the cleaning have access to the toilet rolls so between us ensure there is always a toilet roll out.
Have not had any real problems re the toilet- generally gets a bit muddy on the floors, we use a strip of old carpet leading to the toilet and to kitchen area to try and reduce the amount of mud and renew this after a few months.