Dude, sugar & oxalic acid does not make a detox go any better in my experience with therapeutic fasting, which began in the 1980s when I was in college.
How much fasting have you done in the recent past? How many successful 18, 24 & 48 hour fasts have you done? I generally do 42-50 hour fasts once a week, but I'm not new to this sort of stuff. With only breakfasts & dinners the other 5 days of the week, no lunchs (generally) & little to no snacking.
I recommend that you fast on lots of healthy fats & lay off the listed examples of sugary fruits & spinach the day before. Like loads of avocados, minimally salted olives, some celery sticks, cukes, liberal amounts of fresh fermented foods like kimchi & sauerkraut, kombucha etc.
"Science is not belief but the will to find out." ~ Anonymous
"Culture of the mind must be subservient to the heart." ~ Gandhi
"Who you want to be, isn't necessarily who you are." ~ Ginger/Gina