“What can I do for dehydration?”

Probably the best thing to do is to carry around a bottle of water or a Gatorade type of drink and drink throughout the day. Usually a liter/day is about right, more if you are outside in warmer weather. A crude gauge of your hydration status is to look at your urine. It should be clear in color. If it is dark yellow, drink more.

Unless you happen to have an undiagnosed kidney, endocrine or metabolic disorder that is complicating your hydration status, the only answer is to DRINK MORE. The military learned decades ago that you cannot "train to be dry," and that "salt tablets" as a general concept (limited specific exceptions notwithstanding), do more harm than good. You need to push your intake to the limit of absorption, which is about 1L/1qt per hour. Water works well for the majority of that volume, but if not eating regularly, or sweating profusely, about every third quart should have some electrolytes in it. Some recommend using 1/2 strength electrolyte drink throughout--it depends on the expert and your situation. Even with the best efforts, though, you can still potentially expend more moisture (skin/sweat losses, urinary processing losses, respiratory humidification losses, and GI losses) than the 1qt/hr you are able to absorb--the best way to check this is to weigh yourself in the morning and again at the end of the day (use the same scale). Any weight loss is liquid, and water weighs about 2 pounds per quart (/1kg per Liter)--translate that deficit into your "homework," that you need to make up to be fully hydrated for the next day--with the same 1qt/hr intake limit. Good luck!

Drink more plain water. Avoid alcohol, coffee, tea, and soda. If that doesn’t help, see your primary physician.