I am 25yo japanese male. (yes we exist!) i usually wind up experiencing diarrhoea from overdoing apple juice.

AppleJuice does that: Fruit juice is not necessary. It is better to eat the fruit instead. That is because juice tastes good, so it's very easy to take in a huge dose of sugar that's naturally in the juice. Apple juice has a mild laxative effect. We give apple juice to young children when the children have constipation. The sugars in the juice help the kids go poop. So, drink water and eat some (not a lot) fresh fruit.