Okay, so you might have seen wanko soba before. The gist of the experience is that you go through several trays worth of small bowls of soba – and Yuyuko here, well... they're small for her, I suppose. That is to say, I guess that's what Yōmu's saying there.
Hell 🤨 at first I thought it's a dog joke, and then maybe she doesn't know what a wanko soba is. You know, wanko is "doggy" in Japanese (it means "small bowl" in this soba's context.)
