I've made my breakfast routine more sustainable and healthy with the use of an (oldschool) kitchen appliance. Namely, with a small grain mill.

With it, I can grind cereal grains to various degrees of grinding. For my morning cereal, I grind up about a handful of unprocessed 6-grain cereal the night before and soak it with flaxseed overnight. Combined with some oatmeal and fruit, this makes a healthy muesli. The fact that whole grain products can minimize the risk of disease has now been proven by numerous studies. So just the whole grain, with germ, husk and endosperm contains important substances (especially the secondary plant substances) to maintain health. Along with fruits and vegetables, whole grain products are the most important suppliers of dietary fiber, or rather, fiber.

The whole becomes sustainable by skipping numerous processing and transport processes compared to a ready-to-eat cereal.