electrolyte

It’s so much easier for the body to adsorb electrolyte when you dissolve them in water rather then taking them as pills.

For me I use NUUN tablets:
Great Tasting Active Hydration – zero sugar, important electrolyte, less than 8 calories, easy to use which quickly dissolve in water.

Tips:
Do not restrict yourself by dropping a tab into 500ml of water only.
I drop up to 3 tabs to a 500ml bottle for races so I do not need to carry tabs around me for races. By the time I finish a bottle on the bike, I already have consume 3 tab of nuun. With 4 to 6 tabs on the bike, it will last me through a marathon without any cramps. :)