Hi. Excess of caffeine can cause gastritis
, decreased apetite and you are very right that decreased water intake has caused constipation
But blood in stool
needs to be followed.
I will advise you to consult a surgeon and get P/R Proctoccopy, which is looking into the rectum
to see the cause of bleeding and if required, your dr. will advise you further investigations required.
Orange energy drink does not alter the colour of stool.