The handbook only gives fairly unhelpful advice such as:
SPORT - EXCLUDING: ST
Vehicle settings suited for sportier driving.
Note: Auto-start-stop could switch off when you select this mode.
From my few test drives in mhev Pumas, and comments from owners, Sport increases the amount of regenerative braking.
I didn't notice a great difference, tbh, but I drove diesels for many years so I guess it just felt like "engine braking" which I was used to.
Some owners on here have commented that the regen was quite fierce, though, so I wonder if individual cars vary.
Otherwise sport modes generally sharpen the accelerator response and weight up the steering a little.
Again, I rarely notice a great difference unless driving something a bit more serious with adjustable suspension settings. (I've had a couple of test drives recently in a Hyundai i30N Performance with a!most infinitely adjustable settings and you could definitely tell the difference in that!😀.)
Afaik Eco is the same as in non mhev cars, dulls down throttle response, reduced blower speed in climate control, etc.