Some children are hard to get to take a bath. If your child refuses to take one, agree with them and send them to bed. That night sneak into their room and glue thick caveman type hair on their arms and legs. Glue a prosthetic low caveman brow on their head. The next day when they wake, speak nothing but French to them. Boy howdy, they will think they are so dirty they are changing into a low brow freak that can’t understand the language. I’m sure your child will rush into the bath after that.
If that doesn’t work, the next evening go out and steal one of those giant bugs from atop a pest control vehicle. Place it in your child’s bed and about 2:30 in the morning, flip on your kid’s bedroom light and scream, “MY GOD! IT’S COMING FOR YOU, YOU DIRTY BASTARD! GET IN THE TUB NOW IT’S YOUR ONLY HOPE!”
I’m sure they will thank you in the end.