Taking supplements during a fast isn't really fasting. The way I look at fasting, the whole idea is to let the body metabolize and expel what is already present, not add more stuff. I don't know what length of time you intend to fast, or if you're talking about IF, which isn't fasting all the way, so I don't know if what follows applies. It might be helpful if you edit your question to be more specific.

People fast for different reasons, not just for fat loss, so the term "effectiveness" is going to mean different things to different people. Some want an overall cleanse, some want to restore healthy gut bacteria, some want to give their body a break, and other reasons. Yes, some do it for weight loss, but I think if that is the only goal, the other whole-body health reasons to do it are lost. I can't speak for everyone, but I think most people who fast occasionally do it for more reasons than fat loss, which is a long term process, not short term as most fasts are. It's about regearing the metabolism by clearing everything out, erasing cravings, and clearing the decks for a healthy balanced regimen, which may lead to fat loss.

We're not machines that are easily programmed, so I don't know that there are any silver bullets. Most weight loss from short term (less than a couple of days of) fasting is from water loss. Fat comes later by providing a diet balanced in nutrients that your body metabolizes well, and that isn't the same for everyone.

focus on fat loss first and supplement as desired according to that goal alone. do not fast for the sake of fat loss for that risks taking things to an arguably neurotic level and causing harm to ones self. only in a state of balanced health should one pursue a fast of any length as this is when the benefits of fasting will actually be realized.

Coffee, Green Tea, ALCAR, MCT Oil, Ephedrine, Pseudoephedrine

Any stimulant really...

Guarana and adipex cocktail.......??

I fast for psychological (clarity) and physiological (fat burning) reasons.

I write about the supplements that can help me achieve those goals here.

Depends on why you are doing a fast. If you are fighting a bacterial infection you could "supplement" with some coconut oil as this will make the fast a bit easier to handle. The benefits from fasting primarily comes from restricting protein and carbohydrate. The lack of protein and carbohydrate will starve bacterial infections.

If you want to start protein recycling for any reason, then perhaps coconut oil will prevent that to some degree.

If you want to lose weight quickly, fasting is the wrong end to start at. Fix your diet first (you probably have already); if you are deficient in some micronutrient you will hurt your body more by not eating anything for any extended period of time. Hunger is imo a sign of deficiency so abort the fast if you experience hunger.