Try some or all of the following:
Hills (they don't have to be big ones) - especially so that you can fly back down recklessly;
Riding partners - especially those that you will have to really fight hard to stay with;
A break towards the end of the ride to discuss and solve the world's problems over a well-made flat white or latte.
or I could just stop earlier.
How would shoving brown gunk down your throat make it more enjoyable?