I think chocolate is definitely our best bet, although I'm trying to think of an alternative.

But expanding on the concept of using something that produces large amounts of dopamine, I think a personal guilty pleasure could work even better. I'm not saying people should treat themselves in the morning to $100 worth of opiates, but a so-called 'guilty pleasure' would garner a better reaction than a normal dopamine increase, for example rather than a box of standard chocolates, if you have a particular brand that you really love but rarely get, (i'm thinking thornton's luxury chocolates or something) that would provide a bigger incentive than a box of milk duds.

just an idea