Juvenile jails can have a child wear a diaper if they are incontinent or are wetting the bed.
I remember when I was around 10 years old I was put in Juvenile jail for around 60 days because I was not showing up at school.
So the judge sentenced me to 60 days in Juvenile jail and I had to do my school work in Juvenile jail.
I was a bed wetter and so I had an accident on the first night in and the Juvenile jail nurse lady was very nice about it and said that I could wear a diaper for my problem.
She didn't change my diaper for me but she gave me the diaper and I could change into it in private.
I believe the diapers were the Plastic backed Attends Youth diapers back then.
I'm sure the Juvenile jails still have diapers for kids in their care who wet the bed or have accidents but they probably don't force them to wear a diaper unless they really have a medical need for them and have no control at all over their bladder or bowels.
Even regular adult jails have adult diapers for those who may need them but they don't force them to wear the diaper.