The coworker who stays to finish mopping when they could clock out is one you’ll vouch for for years.

Behaviour after the obligation ends tells you the most. Anybody works while they are being paid and watched, and the person who finishes the job properly when they could have left is showing you something no interview captures, which is why you will still be recommending them a decade later without hesitating. Nobody forgets who left the mess, and nobody forgets who stayed.

Be that person on one shift this week, specifically at the end, when it is tempting not to be. Then say something to whoever else does it, because almost no one gets thanked for it. A reference from a coworker who watched you work is worth having.