Some questions heading into my first fast

Hello. My vacation starts in a couple of days and I figured it would be a good time to attempt a fast without it interfering with my work. My plan is to start in about a week and let it carry on for 72 hours minimum.

A lot of people in the fasting community seem to be doing it to lose weight. What happens to my body during the fast is of secondary concern – my goal is not to lose weight but to explore how fasting alters my mind and my creative processes. Basically I’m doing it out of curiosity, I wanna try it out just to see how it feels.

So now I’ve got a couple of questions which I hope you’ll be able to help me answer:

I am rather lean, would it be better for me to bulk up a bit before the fast in order to ensure I’ve got enough stored energy, should I keep eating at a normal level, or should I ease into the fast by doing some sort of beforehand lowering of my caloric intake? (and if so, is it better to skip meals or to decrease portions?) For reference, and if it helps, some quick online calculations puts my BMI at around 20-21, and my body fat at 10.6%. Early/mid 20’s male.

I’ve read about problems with acid reflux and a suggested remedy has been diluted apple cider vinegar. But wouldn’t this break the fast, since it contains calories? I am planning on maintaining my habit of drinking 1 cup of black coffee each morning, and possibly some black tea later in the day, perhaps this will be enough to maintain acidity levels?

Basically my daily intake will be:
• 1 cup black coffee
• 1-1.5 tsp salt, depending on activity level
• water whenever I am thirsty
• (tea) if necessary, to stave off hunger at dinner time
Does this look like a good plan?

Lastly, when it comes to breaking the fast I see a lot of recommendations for bone broths, meats and animal fats, but for someone whose diet consists solely of foods derived from plants and fungi, what kinds of foods would be best?

Thanks in advance!