If you want to gain muscle you need to work your existing muscles to exhaustion/failure. This will stimulate repair and growth of new muscle cells. To facilitate this work you need to ensure you are getting protein as this is the main ingredient muscle cells. Cinnamon is not needed.

Blood sugar management while exercising is rarely a concern unless you have underlying blood sugar management issues or you are training for endurance.

If you are working out to lose weight high blood sugar is counter productive as your body will preferentially use glucose in your blood stream before it starts to use glycogen or stored fats for fuel. If you are working out to gain muscle, you are trying to exhaust the muscle, adding fuel doesn’t help you achieve that goal. The building of muscle takes place during the rest period, so it is at that point you might want to eat.