Hi Berengaria! The verb 'sacrifice' must always be followed by a noun (it's a transitive verb). What are we sacrificing? In this context, it seems to be sleep! So we would say 'I've never sacrificed sleep'. If you are sacrificing something else so that you can sleep, you could say for example: 'I've never sacrificed MY FREE TIME to sleep'. In this sentence, 'my free time' is a phrase behaving as a noun, so it's OK to follow this with 'to sleep' because the preposition 'to' introduces the reason for the sacrifice. Hope this helps!