There are two approaches to consider

Electrolyte Consumption:

First, as many other answers have already identified it's important to replenish electrolytes as well as water.

Basically, your muscles need positively charged and negatively charged electrolytes to function properly but your body loses them through sweat when you exercise heavily. Positive electrolytes are involved in muscle contraction whereas negative electrolytes are necessary for retraction/relaxation.

There are a lot of different types of electrolytes but sodium and potassium are the most abundant and easiest to supplement. To supplement your own intake you can either look for a pre-mixed drink that contains sufficient levels, by a mix like Emergen-C Electro (it's sodium free so you'd need to add your own), or make your own based on a recipe found online.

Pure sodium is sold as 'table salt' and pure sodium is sold as 'lite salt' or 'salt substitute'. The ratios/recipe can be found by searching online for 'DYI electrolyte replacement drink'. While a lot of 'snake oil salesman' sell high priced electrolyte supplements, the main ingredients (ie sodium/potassium) can actually be purchased in large quantities for very cheap.

Aside: Sports drinks may contain electrolyte supplements but usually contain more sugar than anything. The famous historical 'gatorade' mix that the sport drink was closer to a bitter tasting pure electrolyte mix than the sugar water that's sold in stores today. Food for thought if you're trying to reduce unnecessary carb intake.

Change the way you drink water

The way you drink water is as important as how much you drink. It takes some time (as well as sufficient electrolyte balance) for your body to absorb water. It may feel refreshing to chug large quantities when you're thirsty but your body will flush the water it can't absorb as well as additional electrolytes.

It takes a little time to train yourself to do it unconsciously but it has a noticeable benefit during exercise.

Aside: I learned this from one of my wilderness instructors on a month long backpacking trip across The Superstition Wilderness of AZ.

There are two approaches to consider

Electrolyte Consumption:

First, as many other answers have already identified it's important to replenish electrolytes as well as water.

Basically, your muscles need positively charged and negatively charged electrolytes to function properly but your body loses them through sweat when you exercise heavily. Positive electrolytes are involved in muscle contraction whereas negative electrolytes are necessary for retraction/relaxation.

There are a lot of different types of electrolytes but sodium and potassium are the most abundant and easiest to supplement. To supplement your own intake you can either look for a pre-mixed drink that contains sufficient levels, by a mix like Emergen-C Electro (it's sodium free so you'd need to add your own), or make your own based on a recipe found online.

Sodium chloride is sold as 'table salt' and potassium chloride is sold as 'lite salt' or 'salt substitute'. The ratios/recipe can be found by searching online for 'DYI electrolyte replacement drink'. While a lot of 'snake oil salesman' sell high priced electrolyte supplements, the main ingredients (ie sodium/potassium) can actually be purchased in large quantities for very cheap.

Aside: Sports drinks may contain electrolyte supplements but usually contain more sugar than anything. The famous historical 'gatorade' mix that the sport drink was closer to a bitter tasting pure electrolyte mix than the sugar water that's sold in stores today. Food for thought if you're trying to reduce unnecessary carb intake.

Change the way you drink water

The way you drink water is as important as how much you drink. It takes some time (as well as sufficient electrolyte balance) for your body to absorb water. It may feel refreshing to chug large quantities when you're thirsty but your body will flush the water it can't absorb as well as additional electrolytes.

It takes a little time to train yourself to do it unconsciously but it has a noticeable benefit during exercise.

Aside: I learned this from one of my wilderness instructors on a month long backpacking trip across The Superstition Wilderness of AZ.