Which apricot tree should I choose for a small balcony?

For a small balcony I'd recommend dwarf apricots or espalier varieties, like the Nanetto or Goldrich, which don't grow more than 2-3 meters and adapt really well to large pots. I'm speaking from personal experience since I have limited space on my balcony at home, and I've found that these don't take up all your space but still give you fruit in the summer. The important thing is to choose a pot that's at least 50-60 liters with good drainage, put it in the sun as much as possible and water it regularly, especially right now in July when it's hot. Honestly, if you're just starting out, the Nanetto is the easiest to manage.