Not all of them have rotten hygiene. But enough do so it can make things miserable for a whole congregation.
What we are usually looking at is people that are too busy to brush and floss their teeth (with anything, soap or baking soda work as well as toothpaste) on a regular basis. They are sometimes too busy to take a shower. They get up, race out the door with a cup of coffee, and race to the Kingdumb Hell to reach the 5:30 AM group for field circus. Sometimes they will have a quick breakfast. This is not conducive to good hygiene, and the ones that are most rushed are the most likely to have this problem.
And health problems not related to hygiene factor in. As I know, the witlesses are usually quite sick. They neglect their teeth, beyond not brushing and flossing, to the point where chronic infection comes along. That causes much bad breath. Beyond that, their general health is usually lousy because they don't get enough sleep, they eat fast phude for lunch every day, and they are under constant stress from pio-sneering. Usually, they don't have enough money to really take care of themselves and/or enough sound knowledge to apply. The rags instruct them that they need to wash with soap and water, but that is going to do nothing if the cause of the odor is gum disease or just plain bad health.
More often than not, they need to get to the root of the problem. Regular brushing of teeth wards off gum disease--and I am not here advocating fluoride toothpaste or toothpaste with propylene glycol or glycerine. Baking soda or tooth soap will do just as nicely. Taking a few basic vitamins can go a long ways toward preventing many of these diseases. Eating a decent lunch from time to time also helps--it is the consistent eating of fast phude that creates the problem. If they are fat, they need to walk--uninterrupted, not just to the next door. They also need less pressure to make the next boasting session and arrive at the Kingdumb Hell at 5:30 in the morning for street work.