The couple is undergoing Master Cleanse that involves temporarily consuming nothing but a concoction of water, lemon, maple syrup and cayenne pepper.
It is known as the Lemonade Diet or Maple Syrup Diet, reports The Sun.
Singer Beyonce Knowles used it to slim herself down for a role in the movie Dreamgirls.
Moore said that she is doing it to be healthy, not to lose weight.
The couple revealed their detox diet plan online.
But Kutcher later said that he was craving for 'a steak and a beer'. (ANI)