There are a lot of good recipes for cooking , try looking into eastern european "poor people" quisine like peas , beans, potatos, cabbage etc , easy to make , mostly its just "slice onion , carrot and leeks , fry it in a pot for 5 mins , add peas , cook till they are soft , serve with sour cream"

Many convenience stores sell hard boiled eggs in a ready to eat package. Some special parts of the world have chicken, beef, etc (but not all of us can live in Japan)

The best way to keep your diet clean is to cook at home