I do have a strong reaction to caffeine. I have rules for myself so I don't end up still awake at 3am - I avoid drinking coke (which is what this is really about ) after 6:30pm and don't drink more than 1 a day.
Alcohol is less obvious. I can have a very strong reaction to it on some days and on others I feel like it does nothing at all. I can have some mean hangovers when I drink a lot - they have been known to last 2 days. I haven't noticed if I feel the effects early because I wouldn't have attributed it to that but I will keep this in mind next time. My mood does shift when I'm drinking but all alcohol tends to have the same affect on me; there isn't any variation between them.