Add 1 cup of water and chia seeds to a glass or small bowl and stir until well combined. Set aside and let thicken for at least 30 minutes.
Meanwhile, combine 1/4 cup water with the raspberries and cranberries in a small pot. Simmer over medium heat until broken down and liquid has cooked off, about 10-15 minutes. Transfer mixture to a fine mesh strainer and over a bowl, push fruit mixture through strainer so you extract the juice but not the pulp. Set juice aside.
Add juice mixture, lemon juice, remaining 1 cup water, CocoVia, chia seed mixture and optional sweetener to a pitcher. Stir until well combined.