What is the meaning of "Just for grins,..."?

Same as just for laughs, he did it just for laughs, just for the sake of laughter

I don’t know if you are creating a new expression or misquoting an old one.
“Just for fun, let us put on masks and scare our parents.”
That would mean that it would be fun for us but not much fun for our parents.
“Just for laughs, we could jump into the lake with our clothes on.”
For that to be fun for us, it must be something not usually done, so the people watching will find it f

Thank you very much for both of you!

You might want to check the usual sites for the "just for grins" expression.
Seems to be not too common, but in use anyway.
And it means "just for fun" of course.
I'm not sure if it is one of the typical "borrow" of a German word into the American language,
like Gesundheit, kaputt or Kindergarten. but "grinsen" is a normal German word, meaning smiling but in the
sense when havi