I would say Pray first about the fast.There may be situations or events that make it hard or impossible to fast. Spirit knows and spirit is gentle.
I would not put pass or fail on a fast. Grow closer to Spirit and less dependent on flesh is the goal.
That's just how I approach fasting.
Go into it slowly and gentle and you may want to increase in time.
Please don't try to drive while fasting.
Start with only liquids if new to fasting.
If ending a fast small amounts of easily digestible foods, baby foods work well or something like that. (soups,fruits, what ever works for you)
IMO