Among all other properties, chia seeds help to hydrate, thanks to their ability to absorb up to 9-10 times their weight in water.
Therefore, this is a must after your favourite sport and it is much better than all those drinks with improbable names and colours.

2-3 tablespoons chia seeds 
½ cup citrus juice of your choice (lemon, lime, orange, grapefruit or a mix of these)

Sweetener of choice
Water (2 cups at least)

Pour the chia seeds in a bottle or in a jar.
Add juice and water. If you wish, add a little sweetener such as agave nectar or maple syrup, though is not really necessary.
Mix carefully and keep it in the fridge.
Must be drunk the very day of making.