In this sci-fi scenario/story, they don't use an space walk Astronaut suit (because of costs), but a crappier version of an astronaut suit, cheaper and mass produced.
Due to the technological advancements, the war between troops is basically WWI style: if you get out of the trench, you die, if you stay too long in a trench, you're bombarded. And yes, they are frequently sleep deprived, tired, angry and constantly miserable.
They can remove the suit, the helmet and the body aren't connected, so they can change the suit, but due to the circumstances, they cannot take the suit for more than a few minutes (either to protect them against shrapnel or against chemical weapons). Also, I thought on the helmet having an inside carbon filter instead of focusing on air filters.
For the soldiers, they can't just take out the suit and take a bath.
So, what would be the best way to clean their bodies "on the move" and avoid diseases through months of walking on trenches?
The options I thought was having a small ozone generator that goes around the body, killing viruses, bacteria and oxidising materials, just like we use those in the real world. But ozone can be toxic, specially if thousands of soldiers use those at the same time. And I don't think that they would be capable of cleaning the building up of sweat.
I also thought on a suit inside the suit, were water and cleaning agent would circulate a bit and then be expelled. But I believe that this is too much of a waste of water, not to mention that the remain water in the body wouldn't be able to evaporate to the ambient, because there isn't an ambient. Maybe inserting a ventilation system with a filter could help? But then you need a crapton of filters...
Does a mix of both or just one of these options are good enough, or there is a way simpler method to achieve the hygienic demands of the high commanders of the army?