There's varying opinions. Guys that were doing fasted training did HIIT sometimes, personally I can't do HIIT fasted. I just can't push myself hard enough for my liking.
You can do HIIT postWO. It doesn't matter too much what you ate, as long as it doesn't impede your performance IMO. HIIT is more about increasing the EPOC/afterburn, and increasing your metabolism throughout the day. Intake prior to the HIIT isn't critical.