I am currently taking clen and love it. I have been using it for 1 week now, 2 days on 1 day off at 30mcg per day. In just one week I have dropped 2% bf without losing any noticeable muscle. Yes I am also on a steroid cycle so that helps retain muscle while using a cutting product like clen. My advice is to start low at 20-30mcg per day BC you will def notice side effects at a dose higher than that i.e. Shaky hands, elevated heart rate, increased bp.
As for combining it with an energy drink, there really are no contraindications advising against it. I am a Pharmacist and have access to medical search engines and references that are not available to the general public and after checking these, I feel you are in the clear as long as you limit your intake of said energy drinks as well as staying hydrated. Just remember to constantly drink water and monitor your bp and heart rate. If possible take measurements and post them to the site and I'll review them for you. Take readings before, during training, and 2 hours post training while at rest and post them. I can let you know if you are in the proper range or not. Thanks