Shouldn’t have been downvoted for a question. If people are going to act like Einstein’s with a stick up their ass, they don’t need to be on this subreddit. Keep continuing your fast, you didn’t break it. This sub is all about learning, helping, and pushing one another.
For future reference since nobody actually answered the question wholly, 50 calories is the accepted breakpoint for a fast.
If you accidentally swallow a bug, your body isn’t gunna go oh no protein no more autophagy. Not really how it works. You have to consume enough for bodily processes to reverse or change.
I don’t think anyone can give you a concrete answer because the research on autophagy is still ongoing - it is possible that you broke autophagy with any amount of calories (even if there’s no calories some compounds can be transformed into sugar that the body can use). Regardless, you’ve made it to day 4, I would say you’re fine and just continue on regardless. The best case scenario would be to only intake water and green tea leaves to avoid my statement above. End of the day, it depends on your goal from this fast. Congratulations and good luck the rest of the way!