Yes I have worn diapers to sleepovers as a kid.
What I did was put the diaper on at home before I went to the friends house for the sleepover and I wore the diaper to the sleepover because I was embarrassed to ask to use the toilet at other peoples houses and also because I wet the bed at night.
Wearing the diaper to the sleepover was less embarrassing than possibly waking up in a wet bed sleeping next to my friend.
At my sleepovers with my friends we would share the same bed.
I used to avoid sleepovers because of my bed wetting issue but after starting to wear diapers for the sleepover I was less reluctant to go to sleepovers.
My friends never noticed my diapers on under my pants.
I just took plastic bags to place the used diaper in and place them inside my dirty clothes which I just brought home with me and then threw the diaper away.