The Hot Wheels Goliath can be unlocked once you reach S2 rank and earn enough points (My guess is around 3,000 as i'm currently at 3,505), As long as you pick the right car you can also unlock the Supersonic achievement along with this one.
I did the race in 5:01 using the Hot Wheels 'Bad to the Blade', The tune isn't my own but here's the tune code that i used: 144 940 225 (Shoutout to X Rex Racer for this sweet ass tune)
As long as you do <6 mins Supersonic achievement will unlock at the end of race on leaderboards, and Hot Wheels Legend will unlock once the post-race cutscenes have played through and returns you to the festival where you'll unlock final rank.
In terms of the race itself, it's very simple track and the car i used has immense acceleration and handling as well as a nifty top speed. You should be able to pass all the NPC cars before the first corner. Don't slow down for corners, just turn into them and use the barriers to rebound/exit the corner. If you bump and lose too much speed you can utilise your rewind (I used my rewind twice, both times due to bumping edges on straights). The only part i struggled with was keeping the car straight on the magnetic track section but i think that was the hot wheels stunt support interfering but even without rewinding that section still had more than enough time to make it to the finish line.