Episode 5, since I've seen the first 4 and this wasn't in it. Additionally the title for episode 5 (going by AniDB) is "What?! Your Little Sister Makes Your Lunches?!" which would mean at least part of the episode covers the story in the manga where Funabori physically appears for the first time (obviously since we have this animated screencap). As for why I know that it's just cause I've been re-reading to see differences between the anime and manga, and to catch up from where I had left off.
