I worry about my water use as well; the extra cycling clothing to wash as well means an extra washing machine load each week.
I shower when I get up, then ride to work, about an hour's trip, strip off in the disable dloo and liberally throw water all over myself. It aint perfect, but there are no disabled people where I work, so no one needs to use the disabled loo which ends up with water all over the floor. I keep a small towel at work along with deoderant. No problem.
My boss just laughed when I suggested a shower be fitted. To be fair to him, it's not something he could authorise.