Pointless actually but nevertheless amusing.
Anyways, answering the original query, I drank a couple of energy drinks here and there in a week and increased my intake substantially, in the last week before exam, to give all the effort I could to the exam. I had a severe headache for 2-3 days post exam when I stopped consuming them.
I don’t see taking drugs as “cheating” for CFA exam purpose. People who take these substances are only hurting themselves and it should be of no concern to others.