The organelle that was responsible for the flower wilting is called vacuole.
Vacuoles have the function of maintaining what is called turgor pressure in the plant cells. This provides structure and support to the plant by making the tissue rigid.
When Sam cuts the flower it starts to loose water from its cells and vacuoles inside them, and as a result the rigidity of the flower is lost and it wilties.
When Sam puts the flower again in the water it stars to absorbe the water and the vacuoles inside the flower's cells can provide the tugor pressure again. This is why the plant perks up.
When Sam adds sugar to the water the sugar concentration outside the cell's membrane is higher than the sugar concentration inside, so the cell starts loosing water by a process called exosmosis.
So we can say that what is most likely to happen is that the flower will wilt again.