Smoothies are actually really good at saving time

The process of making it is easy, you just put a bunch of ingredients that can taste good together like protein powder, milk, or fruits. If you don't like how it tastes you can just add more of one ingredient. You don't need to cook it, just blend it.

The ingredients can be frozen and last for a long time. They can also be really cheap, oatmeal gives 1800 calories per dollar, milk gives 2k per dollar. Than you can just add seasonings (cinnamon, cocoa powder, stevia, etc.) that last a long time that are still cheap per serving since you don't have too add that much to have a strong flavor.

Than you can clean it by just blending it with water, eat straight out of it instead of making more dishes to clean. Just clean it by adding soap and water and blending it, and add it to the sink