We are on the quest for the perfect bag and most of us have come pretty close with TB stuff, but what about a beverage container?
IMO, it needs to be
Completely leakproof when closed
Somewhat splashproof when open (i.e. not slosh outside the container when in a cupholder in a moving car/train)
Keep stuff cold/hot for a couple of hours
Fit into most cupholders
Have a decent capacity (i.e. over 20oz)
I've found (and used) this one but it is a bit small and doesn't fit into any cup holder.