Yes. Any sort of flavour (lemon) will trigger your brain to think food is coming so will release insulin.
Insulin release=bad. That’s not clean fasting.
Check out Dely, Don’t Deny OR Fast. Feast. Repeat by Gin Stephens. Both were total game changers for me. She explains how a clean fast (i.e., only water, black coffee or black tea) makes all difference.
Good luck, you got this!