Any grain/starch porridge, oatmeal and congee probably being the most well-known, but it is a pretty broad and international category: https://en.wikipedia.org/wiki/Porridge

It's also a blank canvas so you can add whatever you like, sweet or savory, heavy or light, easier on your own stomach, etc. And very easy to whip together, in bulk if you prefer

Upma or khicṛī are some Indian contenders if you want a specific palette or recipe