Motorcycle Club

You can do this on any race / track you'd like, but the best way is to do it is in a constructors' challenge. Depending which bike you are trying to unlock and therefore riding, they build up their Turbo bar in different ways:

• Superbike: Wheelies - the longer you do one, the more boost you acquire.
• Roadster: Near misses - the longer you can stay adjacent to a wall / opponent / object without hitting it, the more boost you acquire.
• Custom: Jumps - the longer you stay in the air, the more boost you acquire.

You will know when the boost bar is full because it will glow white and a "whoosh" sound will play. Once the bar is full simply wait for a straight or a part of track you feel comfortable with and press and hold  to use up all of the boost. Alternatively, using it directly after you crash is a good idea since you'll cover less distance when using it all.

There is another even easier way to unlock this, it's best done when you are cleaning up if you need it. At the start of any race immediately switch to your Roadster. Do wheelies until you fill up your boost and then press and hold  to slow down while holding  to use all the boost. Even though you'll stop and inch backwards slightly, it still counts as using all your boost. I was able to unlock the trophy with a second account online this way.