Just don't buy those foods. Buy fresh vegetables, tofu, and meat from the edges of the grocery store. Simple. Done.
Simple in theory, snobby in practice. Making food from scratch is a time luxury. It often benefits from good/expensive kitchen equipment unless you want to spend even more time and labor. Let’s take bread as an example. I can buy it from the store for a dollar or two pre-sliced with preservatives and processing, or I can make it myself, which doesn’t really save any money. The fresh kind from the grocery store bakery…
Lesson #1 when you become an adult, bread goes into the freezer when you get home so that it doesn't go bad.