Your hubby will have to be careful he doesn't give himself gas cramps, but apple juice and anything with prunes is a natural laxative. Unforunately, I think if you do too much prune products, it can cause laxative dependency, the same as a chemical laxative (although I think that takes longer to develop). I don't think there's a connection between apple juice and laxative dependency.
Aloe vera pills are also a natural laxative and are considered milder than a chemical laxative, although, again, you can get dependent on them after quite a while. Magnesium citrate is another natural laxative, although I don't think there is a connection between it and dependency. Your hubby might also try probiotics to see if they help; they are safe.
A diet too low in fat can cause constipation. So can bananas.