IMO, one has train your body to drink more water. Keep that radiator topped off. For me it is to drink before I am thirsty. If I have an evening ride / workout / race, I start pounding water early. Additionally, it is an everyday thing, not just I have to ride tonight better get hydrated. If I am not properly hydrated I do drink more during an effort.
Edit: Plus 1 to the above. @MI-XC