February 2017
Fastest isto buy donuts for real money but Im guessing that is not what you want.
Some questlines rewards donuts.
Level up gives you donuts. Everytime you flll the XP-bar you get donuts - even if youre on 939
Daily Challanges can pay donuts - if an event isnt going on - though the reward for finishing 5--10-15 DCs is still donuts, even if the daily rewards are event currency
Sideshow You can award donuts - every 8 hrs in Krustyland.
Actions in Friends towns can give you donuts.
Maggie mini-game pays donuts - every 16 hrs
Weekly Monorail tasks gives you donuts (final pack) if you finish all Railyard tasks within the weekly time limit.
Resets every Tuesday 8 am GMT
Some events have Eastereggs that rewards donuts - check blogs and forums to find them.
I do not recommend any hacks or modifications - in fact I strongly advice against it.
These are illegal and against ToS. You can get suspended by EA and you can get charged in a real court of law.
The mods/hacks can contain worms and you can get your identity stolen along with your bank accounts.