No spaceship should go out in space with proper ways to clean your crew, after long work days and a lot of effort a shower will be needed to refresh your crew , or as needed.
So a new system was added into the game, hygiene. Some activities will decrease it more than others, like jogging around or doing heavy work, while others will do little to lower it.
What's the implication of not being properly clean? well if your crew is injured and have blood loss that may turn into an easy infection. Also it may cause disconfort between crew members, a smelly crew member may affect another one and the other may even refuse to be around because of the bad smell, this will cause stress between your crew members, also crew members that enjoy being clean will be highly stressed if not being able to take baths regularly.
The easy way to keep them clean is to give them enough free time during the day, so your crew will do things like joy activities, baths, eating , sleeping and other things, working is important as well as free time for them.