eca is great thermogenic.
i like to use it in the morning, empty stomach for better fat burning during morning cardio
sometimes preworkout if its been a long day to get through some of the more intense workouts
some days ive taken it with morning or mid day meals to improve mood and decrease appetite
USE IT AS YOU PLEASE, because the calorie burning effects will start within 20 mins and continue for the next few hours and to some extent, the remainder of the day as its clearing your system.
I would take a break though every few weeks, so you dont build up a tolerance.
you can see it really depends on your goals