All of Kambukka's bottles are 100% leak-proof. Yay! But if liquid does escape from your bottle, it might be because of this:
3-in-1 lid: your Snapclean® wasn't snapped into the lid properly. Prevent your bottle from leaking by pushing the Snapclean® mechanism into the lid with two fingers until you hear a click.
Spout lid: your spout lid is not fully engaged. You should hear a click when you close the lid of your spout lid. Otherwise, water may leak through the opening into the spout. But you can sleep on two ears: water cannot escape through the air hole in the lid itself!