for the heck of it

(just) for the heck of it
(just) for the hell of it
(just) for the devil of it

(for enjoyment or no very obvious reason; because it is slightly evil; for no good reason) — просто так; для прикола, по приколу, от нечего делать; бесцельно, ради собственного удовольствия; за здорово живёшь

Use caution with hell

Example: The kids broke the window just for the heck of it.

(just) for a laugh (do sth it for fun or as a joke) — просто так; для прикола, по приколу

Example: When asked their reasons for stealing the car, the boys said they just did it for a laugh.