Homemade plant-based mylk: We can eaily make homemade plant-based milk from nuts, seeds, beans and whole grains! See Nut Mylk Recipes (almond mylk, cashew mylk, pecan mylk, …), Seed Mylk Recipes (hempseed mylk, melon seed mylk, …), Grain Mylk Recipes (amaranth mylk, corn mylk, buckwheat mylk, …) and Bean Mylk Recipes (mung beans mylk).
Soy milk: I encourage my friends to experiment with 2-ingredient soy milk that's sold by multiple brands nowadays. The two ingredients are soy baans and water! Why soy milk in particular? Soy is cancer protective: see Soy & Cancer. In addition, soy has many other health benefits: see Soy, Tofu, Tempeh.
A good shop for buying fresh soy milk in the bay area is Dong Phuong Tofu in San Jose.
Unsweetened: Wheneve I buy plant-based milk from the market (almond milk, cashew milk, walnut milk, …), I look for 'unsweetened' (no added sugars) version. Luckily, soy milk is available as simple, 2-ingredient soy milk (water, soybeans)! So that's another reason I prefer soy milk to other plant-based milks available in the market.
Plant-based milk is a yellow light food! Visit Forks Over Knives Diet and scroll down to see a 3-column table with Red-light foods, Yellow-light foods and Green-light foods. Yellow light foods should be consumed in moderation. Keeping that in mind, we should try to minimize the amount of plant-based milk we consume in the morning — 1 serving should be okay.
Plant-based yogurt: It should be possible to prepare a sweet porridge with plant-based yogurt (peanut yogurt, soy yogurt, chickpea yogurt, …) but I've never tried it. Commercially sold plant-based yogurt have too may additives; I avoid them. But we can make them at home — see Plant-Based Yogurt Recipes.