One interesting dare could be to face a dark side character alone in a spooky setting. It would really test the character's courage.
A dare to communicate with a dark side entity using a forbidden method. This could involve some sort of dark magic or ritual. It would not only be dangerous but also might have unforeseen consequences on the character who takes on the dare, like being influenced by the dark side's power.
Well, there are dares where Harry has to pretend to be a house - elf for a day according to certain fanfictions. It's really funny to see how he copes with it. And for Hermione, a dare might be to go a whole day without reading a book. This is quite a challenge for her as she loves reading so much. These dares add a lot of fun and unexpected twists to the relationship between Harry and Hermione in the fanfiction world.
Another dare could be to confess a secret crush on a fellow classmate. In the world of Boku no Hero Academia, with all the complex relationships, this would surely stir things up. Imagine Deku having to admit his feelings for Ochaco or something similar.
One interesting dare could be for Sasuke to have to wear Naruto's orange jumpsuit for a day. It would be really funny to see Sasuke in such a bright and flamboyant outfit, considering his usual dark and brooding style.
Truth questions can make characters admit their hidden fears related to the dark side. For example, a character might be forced to admit they're secretly afraid of a certain dark side power.
One interesting dare could be for Ginny to try and do a perfect impression of one of Harry's teachers. It would be hilarious to see her imitate McGonagall's strict demeanor or Snape's sullen look. Another dare could be for Harry to fly around the Gryffindor common room on his broomstick without knocking anything over. This would show off his excellent flying skills in a confined and tricky space.
One interesting plot could be where the Pokemon are made to tell the truth about their secret training techniques. For example, Pikachu might reveal that it practices extra hard in a certain area of the forest. Another could be a dare where a Pokemon has to swap its usual moveset for a day, like Charmander having to use Water Gun instead of Flamethrower, which would lead to some really comical and challenging situations in battles or daily interactions.
One interesting scenario could be Naruto being dared to confess his true feelings for Hinata in a very public and elaborate way. Maybe in front of the whole village during a festival. It would be really cute to see Naruto all flustered and Hinata's shy reaction.
In this type of fanfiction, a really fun scenario could be that during a truth or dare session, all the pups are in a circle at the beach. Rocky is dared to clean up all the trash on the beach using only things he can find there. For a truth, Everest could be asked about her first impression of the Paw Patrol team. Also, they could dare each other to do new stunts on their vehicles.
In some fanfictions, a truth could be revealing their first impression of the love interest in the Hunger Games world. It might be something unexpected. And a dare could be to start a rebellion within the arena against the Capitol's rules. This would completely change the dynamics of the typical Hunger Games plot and create a very engaging story.
One interesting plotline could be when Tails gets dared to do a really difficult stunt and Cream is worried about him. Another could be a truth session where they reveal their deepest fears.