Wait, caffeine actually keeps you all awake? It usually just makes me more tired. I only drink it to keep the withdrawls at bay.
The Internet suggests that caffeine might be interfering with your adenosine receptors, and may actually be making you more sleepy.
Try tea occasionally instead. It has other compounds that can offset caffeine effects, even if it also contains caffeine. Or try decaf coffee and see if it paradoxically causes you to be more alert.
I’m British, so black tea with milk (or substitute) and some kind of sweetener to taste is what most of us (and most of Ireland too) go for.
As for which black tea, we don’t really consider that unless we’re at least a couple of levels into serious tea drinking. Most supermarkets sell own-brand and name brand tea bags that we gladly grab every time we’re in a supermarket, but what’s in them is generally a blend made for taste more than anything else.
I am not sure how tea purchasing works in other countries. Sometimes what we drink is called “breakfast tea” or “builder’s tea”, if that helps.