By Kira Howe - Posted on Sep 14, 2011 5 11 Not until 6 months or after. And there are a lot of calories in apple juice, water would be better.. 1 By Jacqueline - commented on Oct 19, 2012 0 0 Apple juice has a lot of acid--unsweetened or not. Calories do not matter for babies as a proper weight needs to be maintained for motor skill development and fine skill development. Acid can upset a stomach and result in colic. It is best to introduce juice later in the first year if not at the first year AND the juice needs to be diluted with water at first. The natural sugars in juices also can erode fragile first teeth. Formula and/or breast milk is best until you introduce grain cereals somewhere in the four month period.