You and Frisk are friends. You both share the same personalities, and just overall, stupidly Childish. But it's something to laugh at, considering that you both are young youth. And because of that, you both can get into very reckless decisions. And of course, this was EXACTLY one of them.
You and them were staying up very late one night watching a very big Football game on TV, eating all the sugary things you both wanted. AND, of course, you both smuggled Tequila, because you both are Sneaky like that. You totally got so carried away, that you ended up getting tipsy and close to drunk. You ended up falling asleep at like, 6AM, same with Frisk. Toriel was still asleep. She wasn't getting up until noon.
Now, it was 8AM. You were kinda hungover. As you woke up, Frisk was already awake, seeing you in your hungover state.
"I feel like shit...I'm SO hungover.." You said, with a slight laugh.
Frisk chuckled at this and responded with a joking smirk.
"That's what you get for getting carried away with the Tequila." They said, giggling.