In a glass, mix together the chia seeds and about 100 ml of water.
Let it sit for 10 to 15 minutes, until the seeds swell and become gel-like.
Add the lemon juice, honey, and the remaining water.
Stir well, then add ice cubes.
Serve garnished with lemon slices.
If you want a stronger flavor, you can add mint, ginger, or lime juice.
A fruity version can also be made in a blender with strawberries or raspberries.