Yes, they can flower and fruit in a container.

James-hoon, does your friend hand-pollinate the tree?

I have a two year old green lessard and it has fruited two crops already, I wouldnt air layer the tree unless you knew it was productive, sugar apple varieties can vary greatly in productivity.

Here the thing, I'm not sure if he know that sugar apple need to be hand pollinate here in so cal, and 5 years ago this tree was under shade from big tree so it didn't get full sun. I think I see a lot of new growth this year, but I'm not sure about flowering. I will check for flower today.

Any way this is my first time air layering and I used sphagnum moss for orchid as median, will that work?

There's a lot of good info on air layering on the web with pics too. I've not heard of anyone doing air layers with sugar apples since they fruit rather quickly from seed. So not sure how well they do during the process and after. If I did do an air layer from that plant, I would take as large a branch as he would let me. Otherwise, I'd just order a grafted one. Go to Ong's Nursery in San Diego. I'm sure he has some.

Has this guy even seen blooms on his tree? Would he recognize them as blooms if it did? Do a search on hand pollinating cherimoya and that will give you the best approach at pollinating sugar apples.

I check with new shoots from cherimoya and definitely that sugar apple has a lot of bloom this year. My cherimoya also start new shoot with flowers, should I prepare for hand-pollinate my cherimoya or just let it grow for another year. I just planted this cherimoya early spring and it still only a stick about pinky finger size with some small short branches.

definitely hand pollinate! don't waste those flowers