Drink water on fast, juice ,tea, coffee,diet drinks but no solid food.Solid food is cheating.If you eat more than very small taste of solid food your stomach will restart and your hunger will come back. I consider eating more than tiny taste of solid food a restart on the fasting.
As said if you can't last couple days on water start off with juice fast. If you can't do even that do intermittent like eat stop eat they have website or fast 5 or warrior diet ..warrior diet has book.
Or practice by missing breakfast for week,then maybe breakfast and lunch,work you way up.
But seriously people get thru couple days of no solid food and rest is easy sailing for 7,14,21,etc. Day 15 here.