[Note: I was writing this as Bejeeber posted his reply.]
Many people use Red Bull. The differences between Red Bull and the smaller energy shots like 5-Hour Energy are (1) It's harder to quickly drink down an 8 ounce Red Bull than a 2-ounce 5-Hour Energy, and (2) even though it is smaller, the 5-Hour Energy actually has twice as much caffeine as the Red Bull. But as I say, many people do fine with the Red Bull. Many people like whatever drink they use to be very cold. As I mentioned, you could also try brewing some strong coffee and keeping it on hand for when an attack comes.
A concentrator is not a good idea. It does not make pure oxygen like what you get from a tank, and usually the flow rate is very low.
In the previous posts in this thread, there is discussion about the kind of mask you have. It is kind of shocking to me that you can't get a non-rebreather mask. It is important when using oxygen that you get as much "old air" out of your lungs as possible, by deeply exhaling, and then fill your lungs with oxygen by deeply inhaling. In a system with a bag, the oxygen is held in the bag until the next time you inhale. With the mask you have, the O2 keeps flowing. That just wastes a lot of oxygen, and I think it might encourage a kind of "normal" breathing instead of the deep inhales and exhales you need to stop an attack. Maybe you could make your own bag, as described here: https://clusterbusters.org/forums/topic/4919-batchs-hyperventilation-red-neck-bag/. It's not the same as a nonrebreather mask, but it would serve the same purpose for you. (Some people think it's not a good idea to keep a bag full of O2 sitting around in your home.)