After he had stormed up to his room, Sans had gone to his bed and buried himself under the covers. He was angry, that was for sure, and his bones rattled with the intensity of the emotions that were boiling within him.
He didn't want to go back downstairs and confront Gaster again. He also didn't want to face Papyrus, either -- because, for one, he felt bad for snapping at him, and for another, he didn't want his own brother to lecture him about his own behavior.
He also wasn't hungry. His own anger and frustration prevented him from feeling any form of hunger.
So, knowing that he wanted to be alone for the rest of the night, Sans took off his hoodie and tried to go to sleep.
Well, more like he tried to force himself to sleep.
But when tried, he did not succeed. He rolled around on the mattress, over and over, trying to get comfortable. But nothing he did allowed him to go to sleep. The only thing he accomplished was messing up the sheets and kicking