My family and I live on opposite sides of the country. My dad likes to come visit pretty regularly, and I used to be concerned at how little he drank. He drank beer, but barely took a few sips of water here and there.
It wasn't until, like, his fourth visit that I realized that he drinks soda. I now stock juice when he visits. Still sugary, but I'm not stocking soda for him. Anything left when he went home would just have to be poured down the drain.
I had forgotten that many Americans just don't drink water. And yes, he is pre-diabetic (but not overweight, remarkably enough).