This is unbelievably easy!
In Hotwheels, just fast travel to track in mid air with no sides and just slowly drive to the edge of the track, letting two wheels go over the edge and simply let your truck fall off.
Seriously, it works!.
Doesn't even matter if you are over deep water either and I'm not joking. I didn't even land the barrel roll as the achievement popped before my vehicle position was even reset after falling into deep water.
Unfortunately, the achievement pop-up doesn't appear in the video below but I can assure you it does work and will probably work with the buggy barrel roll achievement too, but unable to check as I'd already done that achievement some time ago.