Water is necessary for life, just ask the Martians!  Society now has us carrying water wherever we go with a bottle on every desk at work or at the gym or even for a stroll through the park.  More importantly the beautiful Australian weather dictates we consume water at regular intervals.  At an event branded water bottles can be a little piece of your brand in every hand.  Giving it away also stops people wandering off from where the action is in search of their next aqua refreshment!