If there's one slice of life anime series that really didn't need an OVA treatment, then Hyakko is probably it - It was hardly a luminary of its genre after all. Still, at least this OVA in question is only around ten minutes long (bundled as it is with volume five of the manga), so it's hardly a major time sink.
Given its status as a freebie, I suppose it's probably fair to say that this short episode doesn't exactly have a stratospheric budget to burn, and thus this OVA is limited almost entirely to a single location and just two characters, with the effervescent Toraka and bookworm Touma visiting a new cake shop, largely on account of the latter looking for a new quiet place to read near her favourite bookshop after the cafe she used to use closed down.
As you might expect from a visit to a cake shop, the lion's share of the episode involves the pair eating cake, and to be fair this makes for a time to laugh ratio that actually surpasses the series proper. Then again, that was hardly difficult, and so the couple of amusing moments delivered by this episode are hardly the stuff of legend, no matter how much Torako's singing of itadakimasu in an operatic voice tickled me.
I suppose if you enjoyed Hyakko, then this little vignette may have satiated any desires you had for more (however briefly, as it certainly fits in with the mold of the series proper. For me though, it was more or less a reminder of the wasted potential of that series, and how it has consistently failed to live up to any such promise almost from beginning to end.