Though most people consume caffeine in the morning, Ayurveda recommends the consumption of warm water. One should have a glass of warm water (ushnodak) in the morning. It enhances peristalsis (movement of the intestine) and also flushes the kidney of any harmful toxins and free radicals.
In certain conditions, depending on Agni and the season it is advisable to consume things like aloe vera/apple cider vinegar/ ginger, mint, fennel infused water, etc, which should be 15-30 minutes after the warm water.