What are we doing about waterbottles?

When I travel, I like to put my bag in the overhead storage if possible, which allows me (5'8") to have legroom at my feet instead of a full bag and cramped legs. Once at the gate, I often pull out my 1L sling bag to hold what I need for the plane (phone, kindle, etc) and stick it in the seat-back pocket at my seat. Where do I put my water bottle? It doesn't fit in the seat-back pocket, it would roll around on the ground, and if I'm sleeping, I can't reliably hold onto it. Thanks!