As long as you're not super skinny already, a three day fast is not difficult. Drink water, black coffee, and green or black tea (no sugar or cream added). Have some good pink Himalayan salt on hand and use a bit of that on your tongue if you get really hungry. You want to be sure to get your electrolytes, so mineral drops like these are great to add to your water. Don't drink any flavored waters, the flavor will often make you ravenous.

The fasting subreddit has a great wiki. You can also check out Dr. Jason Fung on YouTube, he has a very informative channel on how to fast, and the science behind it.

Let me know if you have any questions. And remember, hunger comes in waves. Stay busy and it will pass.