It's been awhile since I read the Dressrossa Arc, so it might be in there (but I skimmed it and didn't see this specifically mentioned), but I was wondering: does Sugar turning someone into a toy make that person unable to use their devil fruit? Not to, like, hurt someone (since she basically uses the 3 Laws of Robotics) but in general/for day-to-day things?
It's hard to say. Hypothetically, a toy could still hold a devil fruit power since Dr. Vegapunk made it possible to give items devil fruit powers. However, the only Devil Fruit holder turned into a toy was Robin. Robin is seen very little as a toy: just right after she becomes one and the following episode (episodes are manga, but she is seen just as much in the anime). If Robin could use her power, her arms would likely be weak toy arms, so she never even tries to use it. This ultimately means we can't yet know the answer for certain and as far as I know, nobody has asked Oda. Both answers are equally likely.
I may be wrong on this but I don't think we have ever seen her powers used on someone with a devil fruit and as a result we never see any manifestation of devil fruit power nullification. Because of this I would have to say her powers do not nullify devil fruits as there are no mentions of it in the anime manga or wiki. The link below is to the One Piece wiki where you can read about her abilities. http://onepiece.wikia.com/wiki/Sugar