Forced suppression of all cravings including harmless ones
Are there any karmic consequences from the harmless consumption of a slice of cheesecake? And why?

Cheesecake is just food. All sentient beings are sustained by food. Sentient beings are not sustained by wishes. Suffering is sustained by wishes. So don't wish for the cheesecake, just eat it if it's there, sharing it kindly with others.

Should ... forcibly suppress all their cravings

Generally speaking, suppressing a craving just makes it stronger. 

But you can restrain or relinquish. Just observe the rise and fall in the five grasping aggregates: form, feeling, perception, choices and consciousness.  That craving is impermanent and is not your self, it is not yours, it is not you.

...however...

If you cannot muster any skillful thought, then desperate measures are called for as described in MN20:


  With teeth clenched and tongue pressed against the roof of the mouth, they should squeeze, squash, and torture mind with mind.


Perhaps that would be overkill with...cheesecake?