Definitely not just your bub! DD started daycare at about 9 months old, and was going four days a week from 8-3. I was sending her with three sippy cups with 100ml in each one. She'd barely have half a cup if she had any, so I decreased the amount. It was frustrating because as soon as she got home with DH she'd immediately down 200ml.

In the end, I just stopped stressing. I give her a big feed before dropping her off, she has plenty of food and water while she's there, then she catches up at home. I realised she wouldn't starve herself, it's just different at daycare and she's so busy, she hasn't got time to sit down for a big drink lol. Plus it's nicer coming direct from me

So now I send her with three cups, each with 50ml. Today she drank the lot but that's rare. But like I said, it's not causing issues and she's doing fine