PowerPoint is a little bit weird. On one hand there is no hard space (ctrl + space, ctrl + alt + space do not work). On the other hand, however, inserting hard space from num pad works. PowerPoint NOT ONLY inserts this character but INTERPRETS it right – so keeps word after it together with the word before hard space.
To insert hard space:
alt + 0160
(keep alt pressed and press on numpad ‘0’,’1’,’6’,’0’ and release alt).