Preheat your oven to 350°F (175°C) and line a large baking sheet with parchment paper.
In a medium mixing bowl, whisk together the dry ingredients: rolled oats, flaxseed meal, chia seeds, vanilla protein powder, brewer's yeast, ground cinnamon, and sea salt until well combined.
Add the egg whites, vanilla extract, and water to the dry mixture.
Stir the mixture vigorously with a spatula until a thick, uniform, and slightly sticky dough forms.
Divide the dough into 4 equal portions and place them on the prepared baking sheet, pressing down slightly with the back of a spoon to form thick discs.
Bake for 10 to 12 minutes, or until the edges are golden brown and the cookies feel firm to the touch.
Remove from the oven and allow the cookies to cool on the baking sheet for at least 5 minutes to ensure they set properly before serving.