Absolutely going to break the fasting cycle.
If you’ve been on the 16:8 for a while, a moderate amount of calories (less than 5) will almost never take you out of ketosis bc it’s such a drop in the bucket that your body won’t release insulin.
Additional note: things like amino acids even though they can be zero calorie will still shut down the fasting process. Same for monk fruit and any “zero calorie” sweeteners.