none, using supplements will counter act the point of the fast which is to stress the body and train it to get stronger in the first place. it would be like doing pullups with someone under you helping push you up, you won't get the full benefits
the only thing you can take it pure electrolytes like salt or potassium only IF you are sweating, but you shouldn't be sweating during a fast either. if you want 100% benefits no working out or exercising during a fast either, this allows your body to heal itself. you CAN exercise during (i have before) but you won't get the healing effects.