Hi,
I found a company that sells pure vitamin powder called BulkSupplements. You can buy from them off Amazon (here is the link for Vitamin E:
https://www.amazon.com/BulkSupplements- ... 0YOMA?th=1.) You can click around to find the rest of the vitamins you are looking for.
Putting the powder in water and putting an apple in should work. Indeed, the apple itself is a combination of antioxidants and water. HOWEVER: only Vitamins B and C are water soluble. Vitamins A, D, E, and K are fat-soluble only. So this would really only work with Vitamins B and C.
Apples would work! They are also rich in Vitamin C.
What is your approach to this experiment? You could possibly try to see how long an apple slice takes to brown by itself (Vitamin C) and then dip it in another vitamin and see how much longer the apple survives (subtract the added-vitamin-browning time from the the plain-apple browning time). Just an idea!
Here's a link to the ScienceBuddies Antioxidants project idea:
https://www.sciencebuddies.org/science- ... tioxidants.
Good luck on your experiment!
Saanya