(just) for the heck of it
For no particular purpose or reason; only for the sake of fun or distraction. People don't call me Mr. Green Thumb for the heck of it! There's a group of kids who go around smashing car windows for the heck of it. Just for the heck of it, let's order dessert first.
for the ˈheck of it
(informal) just for pleasure rather than for a reason: ‘Why are you doing that?’ ‘Just for the heck of it.’