I know it is very different for different people. If I don't have caffeine for a couple weeks, I lose my ability to function. For example, I can't show up anywhere on time.
I should have probably clarified I am functioning better than I would be if I was on prescription medication. The caffeine and the choices above really help. However during periods of heavy stress it isn't enough by itself. I have also had to learn to be comfortable with a lot more uncertainty than most people because I literally can't cope with the stress.
But again, I was medicated with a number of different medications for years I can no longer tolerate reasonably. So it is perhaps for the better.
As for your question
I avoid alarm clocks because I find that waking up suddenly seems to make my ADD worse. I use them occasionally but maybe a few times a year....