I have been doing a lot of research on fasting and everything I've read has advised against taking anything except distilled water according to thirst.
If you drink tea it could possibly trigger hunger and the digestion process. The reason for a fast is to give your organs a time of rest and repair, anything other than water would disrupt that process.
As for vitamins that answer is also a no! I have read the book "Fasting For Health And Long Life" in the book the writer quotes another authority on fasting, Shelton
states: "We have no means of knowing how much of a reserve store of vitamins the body possesses, nor do we know where all these reserves are stored. But we may be sure of one thing, namely, that these stores are sufficient to outlast the most prolonged fast."
It might help you to read Shelton's book:
Hope this helps, and good luck with your fast. Maybe Chrisb1 will post in this thread, he is most knowledgeable on the subject of fasting.