What are the pros and cons of an adult trying an energy drink?

I’ve only had one. It was when I was four and it was a Jolt cola. It said that it has twice the sugar and caffeine from a cola beverage. It hurt my arms, and I haven’t had one since. What are the pros and cons of drinking an energy drink? Also when in the day is it best to drink one?
I am thinking of trying one at the morning of my English comprehension exam for 3 hours in a year or so from now.