Asphalt 8: Airborne

The easiest way to get this is to work through the seasons getting stars until you get to season 6 or 7.

Once at least 6 is opened up, continue to play until the 100% credit bonus is in effect (5 straight days of playing IIRC).

With both of those in place, choose an event with relatively easy star requirements (I picked 'Fr. Guyana Rev. Class A Classic' from season 6, where for 5 stars you only have to come first, have no wrecks, and have 6 perfect runs).

Choose your fastest car (at this stage, I have a close to maxed McLaren Spider, which is incredible) and start the race.

Do the best you can to get all 5 stars on the race, and if you're getting towards the end and it doesn't look like you will do it, I found that pausing and restarting the race without returning to the menu maintains your credit bonus for that days race.

Once you get 5 stars, the cash you get from that coupled with the credit boost effect will easily see you over 10k credits. I actually got 17k in a race doing it this way.

I expect you may be able to do this on an earlier race, but I have found that the higher the class requirement for the race, the more cash the stars are worth.

On the same score, in the earlier seasons you are unlikely to have a Class A rated car that is good enough to easily win the race, so season 6-7 (depending on what event/car you wish to use) seems to be the sweet spot.