Foggy is sleeping with Daredevil, not knowing Daredevil is Matt. (Up to the filler how that works. Blind folds? Really dark apartments?) Can be as dark (or not) as the filler wants.

Bonus points if Daredevil asks if Foggy is with Matt. Foggy lies and says he doesn't like Matt like that. So when Foggy finds out that Matt is Daredevil, that's the lie he's talking about; Matt knew Foggy likes Matt and said nothing.