Ceylon Cinnamon sticks makes the best Cinnamon extract. This is mainly because Ceylon Cinnamon is sweeter and less spicy than the common Cassia Cinnamon you get in US stores. The soft Ceylon Cinnamon sticks also have more oil in them compared to the hard Cassia Cinnamon making it far more suitable for making Cinnamon extract.
When blended with light Rum, the aroma of Ceylon Cinnamon is shockingly good. It's refined and sophisticated. Very much like an expensive perfume. A flavor and aroma that is exotic and soothing. This is why the leading chefs of the World prefer Ceylon Cinnamon for making fine desserts and baked goods. It also has lower Coumarin content, an added benefit.
You can of course start with a dark glass bottle but you can't see the color to check your progress. Only about half the bottle will remain as you remove the Cinnamon sticks since the some of the alcohol will get absorbed into the sticks and there is no way to squeeze it out and some alcohol will tend to evaporate over time.
Putting the contents into a darker glass bottle will maintain the efficacy of the Cinnamon for a longer period. Strictly speaking this is not necessary if you tend to keep the extract in a cool dark cupboard. Never refrigerate. A cool dark place is always best.
CINNAMON OIL VS CINNAMON EXTRACT
Cinnamon extract is derived from extracting the cinnamon flavor including a small amount of oil content via an alcohol based solution like rum. It's far less potent than Cinnamon Oil but far easier to use for cooking.
Of course you can use Cinnamon Oil in food (like Apple Candy or baking) but most people just don't have the skills to mix it properly because it is extremely concentrated.
If you do decide to use Cinnamon Oil in cooking, then you should ideally use Cinnamon Bark Oil which is very refined and sophisticated and suitable for internal consumption. But because it far more potent you would use a small fraction compared to Cinnamon extract.
We use Cinnamon Bark Oil in our tea for example, but this is professionally mixed. The aroma of Cinnamon Bark Oil is truly exotic, but be careful how you mix it. We cannot give you recommendation on the mixing ratio but less than 2% would be a good rule of thumb for Cinnamon Bark Oil. It's that potent.
Cinnamon Leaf Oil is not suitable for internal consumption because even the best quality Cinnamon Leaf Oil can be quite harsh on your internal organs especially if you mix it wrong and put too much. It will burn your insides.
For most cooking especially baking, use freshly ground Cinnamon powder or make your own Cinnamon extract.