Question about Fat burners

Alexandra
Currently started taking 212 fat burner two days ago. I never drink coffee or have any caffeine. The first day I felt energized and couldn't sleep at night. Second day I felt like I sweat more in gym, but I was exhausted at night. Today , say three, sweat more at gym, but I don't feel energized. Very drowsy and tired. Been eating heathy, and drinking lots of water. Also I feel bloated. 
Anyone taken fat burners? How did it make you feel? Is it normal since I'm not use to caffeine? Did u feel bloated? 
Any suggestions on a better fat burner?
Thank you!