thats your choice really. officially your supposed to refeed but saying that you might get away with it if you dont. i had a slice of cake once and it didnt make a bit of difference and still had a good loss at weigh in that week but everyone is different. that said, it can be difficult to get back on the diet once youve eaten something so beware. also, do not whatever you do, drink alcohol as you might make yourself ill..you have to reintroduce it gradually once you finish the diet (just from other peoples past experiences, i wouldnt want you do go down that route and have to visit the hospital)!
hope that helps a bit
h x