Training with Hinako sold really well, selling out on release day, so Studio Hibari, the company behind the first OVA, decided to make a sequel to capitalize on the first, releasing it a quick 7 months after the first. This time around, instead of exercise, you're now falling asleep with Hinako, assuming that you're all tired out from the exercises from the first one. Or you're watching her as she sleeps, depending on what you're doing under those bed covers of yours.
Much like the first OVA, Sleeping with Hinako is a few bits of original animation, like Hinako talking to you while you're both in bed, a few moments from the first OVA followed by on a scale to see if she's losing the weight, to her brushing her teeth, her dreaming about snacks, and her getting up to go to the fridge to get snacks, only for you to catch her in the act. But most of it is reused animation, mostly of Hinako sleeping (obviously). It doesn't look bad, but you can tell the budget went into a few of the scenes, and then some of it was copy and pasted until they had something long enough to press to a DVD.
It doesn't even have the interactivity of the first one. I imagine that this was released on an even tighter schedule to try and get something released to capitalize on the success of the first one. I guess you could call it a step down, but there wasn't much going on in the first one, so it's more like shuffling in place then a step down.
There isn't too much to say about this one. Once you've read the description, you've got the gist of the OVA is about, and it's pretty obvious what this is and what it's trying to do from the DVD cover alone. I guess if you're a big fan of "Training with Hinako", then this is for you. But for me, it's the weakest of the three Hinako OVAs. It has a few cute moments here and there, with the going to the fridge in the middle of the night being the best part, but most of it is just watching the same animation of someone sleeping.
All of this sitting in silence watching this makes me wonder the logistics of the world, if more people have been sucked into this anime world, or if Hinako is the only. I was so underwhelmed with this that my brain started trying to figure out the logic behind it just so my brain had something to do.