if you must or if it helps the long term sustainability of your fasting, absolutely go ahead and do it. 10-15 calories non-carb would fit into the “dirty fasting” realm, not “ideal” but certainly not going to have a big effect on your progress.
I should have rephrased,, as I seem to have struck a nerve with the technical term “fast”. I am new to this so I appreciate the education and more so your patience,
I thought I read somewhere that there was a 50 calorie window or something. But I must have read or misunderstood it.