Question: Having committed to the Eight Precepts, is it permissible to drink coffee after mealtime?
Answer: Although different Buddhists might have different views on this, according to the spirit of the precept, of not consuming food after mealtime, this should not be permissible — unless that precept has been given up formally, by first informing another Buddhist who understands about the precepts.
This is so as coffee drinks are made from beans, and are thus filling to some extent, making them foodlike. Likewise applies to beverages like soy milk, grain drinks and such.
That said, drinking plain tea is alright. However, if there is craving for tea, in the spirit of the precepts, to reduce even subtle greed, (hatred and delusion), drinking only plain water would be even better.
Eight Precepts Ceremony (For Precept Recipients)