Oh dear. I would not hold out too much hope for this poor tree. Firstly, these resent being transplanted however careful you are. Magnolias and their relations have big fleshy roots rather than many fibrous roots and they are slow to regrow. If the roots were not conserved it's going to be even less happy. Secondly, cutting most of its branches off was an unfortunate move. It is a long held gardening myth that reducing top growth promotes root development. Sadly, it doesn't. It forces the tree try to make replacement top growth from dormant buds, not roots. Transplanting - Should You Reduce Top Growth? (gardenmyths.com)

But it's done now. All you can do is keep it well watered and cross your fingers. And I'd not give that 'gardener' any more important jobs. Also you don't give your location. Is it a good time of year to be transplanting trees where you are?

Thank you dear! I’m in Los Angeles, CA (zone 10b).

' Will sugar water solution help? '

If you're talking about watering the tree with a solution of sugar and water the answer is no.

Somewhere along the line, someone has concocted the idea. that if a plants roots manufacture sugar from nutrients in the soil, then giving the plant sugar directly into the root zone, is somehow a good thing to do. This is just not true. Adding something like sugar can start a culture of bio-organisms in the root zone, none of which is beneficial to the plant and can actually kill the plant.

https://www.thespruce.com/using-sugar-water-for-plants.

”Oh, dear.” That is exactly how I was going to begin my reply, lol. The worst offense is the top pruning!