You would not put junky fuel in an Indy race car and expect it to perform. Your body's no different. So if you're eating junk, stop. If you're already eating good quality foods great! Keep going.
The thing I did in training that took me from size 20 relaxed fit jeans with elastic to size 12 (besides ride lots) was "eat food made from food". If I don't recognize the ingredients, can't pronounce it, I don't eat it. I dropped a lot of inches in that time and weigh nearly the same.
In general if I've seen it on TV or worse on a Super Bowl ad it's probably not good for me.

I'm not a vegan or even vegetarian, I eat a variety of foods. I just try to eat food that's made from food.
When it comes to the post ride meal you do need to eat after a workout. You can find what fuels you both physically and emotionally (as in "that was tough. I deserve a big treat").