Alright so firstly, the game is confirmed to take place between FNaC 1 and FNaC 2,(I think Aurus confirmed this but I can't be fully sure) so Im very sure we will be against the new animatronics from FNaC 2 but the question is :Why is Sugar here?

Well my theory is that Sugar is the Candy from Five Nights at Candy's 1 it's a kinda far fetched theory but bear with me here, I think maybe the company was being stingy and used a few of his parts for the new animatronics which is why Sugar doesn't have the red cheeks and tie that he had in the first game.

So overall, I think it's like what fnaf 2 done with the withered animatronics (though they wouldnt have taken as many parts from him like other animatronics such as Withered Bonnie.)

Thanks for Reading, have a great day! :)