If you use any of them on yourself, you get bad endings.
Intended use of them:
WG: Use on Nicole (Shadowed Curios owner).
BE: Use on the Sweet Cravings baker.
AE: Use on the waitress at the all-you-can-eat cafe.
Hyper: Use on Kali at work.
Cinnabuns are just something you can eat, but the to go one is used to fatten the clothing store owner. Bring one and give it to her every time you visit the clothing shop and eventually she'll gain weight.