Diet soda causes inslulin spike?

I've heard Goatis say that and maybe Faceiq too, is that true or not, Chatgpt told me it does not it's only "cephalic phase insulin response," meaning your brain anticipates sugar and drops a microscopic amount of insulin just in case, it's like negligable amount, Is it ok if I pepsizerosugarmax while fasting to ease the fat loss (it really works for me), I don't care about other negative effects, just does it cause insulin spike to any significant extent to affect fat loss or is it harmless in that particular regard?