OP asks for caffeine alternatives... over 50% of the replies contain some form of caffeine (milk tea, tea, caffeine tablets lol)
coffee and tea have roughly the same amount of caffeine
i used to drink a lot of strong tetley orange pekoe-the kind where the pod that stays too long. it's gotten to a point that drinking that makes me sleepy so it doesn't really work long term.
what i've tried is if you're feeling a little tired just run up and down the stairs a little to get your heart rate/adrenaline going, can keep you up for a bit, but nothing is better than getting QUALITY sleep