Imagine the boys playing "never have I ever" in Kaer Morhen one winter and both Geralt and Jaskier are using extremely specific senarios to make each other drink like
"never have i ever gotten severely injured during a griffin fight and refused to do anything about it until I was forced to by my bard BFF"
or "never have i ever hooked up with a butcher, his sister, his wife, his two sons and daughter in the span of a week"
while Lambert, Eskel and whoever else is present just watch with amusement.
Of course the whole thing ends with them getting blackout drunk and making out.
“Oh gods are they kissing?” Eskel asked, throwing his arm over his eyes to block out the sight of his middle brother and the bard. Lambert guffawed.
“Terrible! Disgusting!”
“Shuff uff,” Jaskier slurred, gesticulating at them with one limp wrist. “Go aweh.”
“As you please, Milord,” Lambert snorted. “C’mon Eskel, let’s get out of here.”
“I need a dip in the stream to clear my eyes.”