Not all babies will drink prune juice. I know one Mum who cooked and pureed some pears.
You can also give diluted Orange Juice but not close to giving your baby milk (breast or formula) as it curdles the milk and baby is like to vomit juice and milk up. You used to be able to buy special baby juices in a bottle that you took off the lid and put on milk bottle top and teat. I haven’t seen it around for awhile.
Published 27th January 2020