Simple Modern Water Bottle with Straw Lid Vacuum Insulated Stainless Steel Metal Cup Bottles | Reusable Leak Proof BPA-Free Flask for Gym Sports | Summit Collection | 22oz, Midnight Black

Thermos Ultralight 1l. They don't make it anymore, but it was incredible. Held ice in water for 30+ hours. After that, my fave is the Simple Modern Summit, the 1l also holds iced water for 24+ hours. I've been trying the Mesa for a few months now, it's their Owala FreeSip competitor, but it's not as good as the Summit, sadly.