You don't need insulin to get you into ketosis. Thats a dangerous game IMO. If you are following a TRUE Keto type diet, and you did a "refeed" for a day, it will take you about 3 days(average) to get you back into ketosis, depends on the person. If you only had 1 cheat meal and you are not back in ketosis the next day, then you were probably not in ketosis to begin with. If you post up you daily diet, we could help you a little more.