A funny thing always happens to me when I go to sleep after excessive exercise: my dreams revolve around drinking copious amounts of beverages. I've dreamed of opening the refrigerator and drinking dozens of consecutive Gatorades, knocking over a vending machine and drinking everything inside and sitting down at the kitchen table and finishing an entire gallon of orange juice.
Riveting, I know. While the plot line is pretty lame, what makes these dreams interesting is that they show a clear link between how I'm feeling physically (very dehydrated) and what is going on in my mental dream state.
Dreams are difficult entities to study because of their subjectivity. You can't scientifically determine exactly what someone is dreaming, and thus interpretation can be biased by the interpreter. Dreams are also personal – the same dream might mean one thing to one person and something entirely different to another. Countless sleep studies, however, have sought out (and found) connections between physical factors and dreams.
For example, room temperature and body temperature can affect the quality of REM (rapid eye movement) sleep, which is the sleep stage during which you dream. Elevated body temperature has been found to potentially increase nightmares. Additionally, several studies have found that the introduction of sounds while sleeping can also influence dreams.
Perhaps most interesting is that several studies have even found connections between sleep positions and dreams. One study, for example, found that left side sleepers have more nightmares.
The good news about study findings suggesting that dreaming and sleep quality may be affected by factors such as temperature, noise, and body posture, is that these are all factors that we can control. Start by getting yourself a brand new water pillow, which will adjust its waterbase as you move to keep your neck and spine in a normal, healthy position – eliminating pain and discomfort while sleeping.
While it doesn't seem possible to ever be in complete control of your dreams (which is part of their charm) if you make yourself as physically and emotionally comfortable as possible – eliminating as much physical and mental stress as you can – odds are, you are setting the stage for sweeter (and maybe less thirsty) dreams.