Okay headcannon time
Todoroki and Dabi do not sleep. Whatsoever. This is practically canon at this point but here's the thing that I'm adding.
They will only sleep under very, very specific conditions
First, they both have to have someone with them.
Neither will sleep in public spaces, such as the living room couch. Because of their childhood they are uncomfortable being so vulnerable in an open space
Both have to be dragged into bed sometimes because if not they'll drink an insanely unhealthy, maybe even ungodly amount of espresso and stay up forever.
Neither can stay asleep for longer than maybe an hour
God awful nightmares from hell.
For Todoroki, who's been pretty much left by everyone, he has to be sure that the person he's laying with is asleep first. His reasoning is that it ensures that, unless they wake up before him which is highly unlikely, they'll still be there by morning.
He has to have his specific blanket, because Fuyumi hand sewed it and it made him feel safe.
It had to be after a certain time, because he was used to being woken up as soon as Endeavor got home from patrol for training.
He's little spoon, it makes him feel safe and protected and he needs it.
For Dabi, he's big spoon. Growing up with three little siblings, all of which he was used to at least trying to protect, he had a major need to protect. Even if he could majorly benefit from being the protected one, and would probably feel a lot safer and more happy if he let his guard down, he refuses to. Instead, he's always on the outside so he's always ready to protect.
Will not sleep at night time. That is a ginormous no go for him. He always feels like that's when he's going to be attacked, that's when he's gonna be brought back to his awful childhood
