Babe is 10months, how much Apple juice to give for constipation?

He poop once to 3 times a day. Hard big pellet poop. I changed his diet. He is drinking 3oz of water and he is drinking great. Also what brand of apple juice works for you. Traditional ways to help constipation did not work too. It’s been bothering all of us now because he wakes up crying at night to pass a pellet poop. He does not like prune juice so I wont go that route. I offered pear fruit steamed and fresh but don’t like it either. He eats a or of fruits and vegetables too. He is using Kendamil for 5 months now. Everything changed poopwise since solid. I’m desperate for help.