i would recommend starting slow if you haven't done it before. go 1 day without food, then 3, then 5, then 7, then 2 weeks, etc. i've done this many times to lose weight and it's very effective. my longest has been 1 month without food, just consuming near 0 calorie things so i can get some electrolytes and not die. i wouldn't recommend this, but i also did insane amounts of walking on a treadmill everyday and nearly fell off multiple times, but i don't think it really helped much at all so it's probably not worth it. you'll probably lose about 4 pounds per week without exercise.
the first couple days are the hardest, but then it's like smooth sailing. you will feel tired, your sleep will suffer, you will feel weaker, but that shit is obvious. the hardest part is if you think about food too much your stomach produces excess acid that can lead to nausea and vomiting. i would recommend having emergency food around that's basically 0 calories, like chicken broth or pickles to help soothe your stomach if that happens. for sugar cravings, i would also have stuff like Gatorade Zero around so you can get the sweet taste without consuming actual sugar. also remove any other food from your home if you can to remove any temptations.