depends on the tenacity of the child! It might only take 2 days - or as soon as they realise you are serious.

It's hard to know if to give something else...cos it's sort of like giving in again but haaard to do. I gave mine a piece of buttered bread (i'm not sure how to make gruel ) but nothing else.

One thing that is BRILLO (imo) is that she will eat everything otherwise.
Another good tip - Nelle gives her boys dinner at lunch time so she knows they have had a good hearty meal at least once a day.

GL