Prune juice is often used by humans as a way to help with constipation as often once you drink it you will have a more regular bowel movement. However the question is can guinea pigs drink prune juice?
No, it isn’t safe at all for a guinea pig to drink prune juice.
It is far too sweet for them just like if they were to eat prunes. It’s just too sweet and not good for their health.
If you want a healthy choice you should stick to giving them water unless your vet were to prescribe another liquid for your piggy.