The best advice I can give you is to be patient.

My sugar apples (actually all my anonnas) were slow starters too, now that they have some trunk size they grow like weeds. One put in ground in 2012 is being caught up in size by one planted in 2014. Previous years I hand pollinated both, this year I stopped hand pollination and the smaller 2014 tree (9-10') has set a boatload of fruit while the larger 2012 (12' tall) has bloomed but not set one fruit. Both get identical care and light being only 8' apart.

gnappi, thank you for your advice! I can't wait 'til they get bigger. I have them in partial shade under a tree right now because I'm afraid the 80-90 temp in direct sun may fry them. I thought they were going to die this past winter. We have about 2 weeks during the winter with morning frost and all of them lost their leaves and I wasn't sure they were all coming back but they did!

Interesting! So your smaller 9-10' tree set a boatload of fruit while the larger 12' set zero fruit and get same care and light. I assume they are seedlings - are they from the same fruit? The smaller tree probably just have stronger DNA.

No actually, I bought the second one from a different grower because the first was (and still is) being lazy about producing fruit. With well thought out tip pruning they are both very handsome trees now, nicely full and they provide shade on the west side of my house during the hottest part of the day.

That reminds me of my cherimoya trees. I have 4 seedlings. 2 are almost 2 yrs old (3' tall) and other 2 are 4 yrs old (4' tall) but the trunk are not as thick as the younger trees. The 2 older trees - the owner said the mother tree did not produce much fruit - that should of been my clue to step away but I was desperate to have cherimoya trees and I didn't want to waste my 1/2 hour trip driving there. The 2 younger trees are from the same person and seemed more vigorous and faster growing than the 2 older trees. I can't wait to get fruit. I know it's another couple years. All are pretty leggy. Should I heavily prune them to try to them to grow bushy? I've only prune them a little bit.

They are not like mangos, and pruning heavily may set them back even further.

From my limited trial and error experience I tip pruned (NOT the whole branch) 6"-12" of the branches I wanted fuller. Branches that sprouted where I did want more branches I cut off completely.