Actually I Have Thought Of This Many Times But The Series Might Have A Point. This Kind Of Water Comes From Different Parts Of The Pokemon Body So It's A Body Fluid Just Like Saliva 或者 Sweat. So It's Like Being Thirsty And Waiting For Someone To Sweat 或者 Spit Just So 你 Can Drink. Still, I Don't Think It Has Ever Been Clarified. It's Just A Theory !!!!