All of the above is great tips. For me personally, it's also been about subtly changing the mentality or aesthetics of what a "simple meal" has to look like, because I think a lot of us who are struggling have a tendency to unconsciously "punish" ourselves by reinforcing the depressive vibes. It's a DEEPLY Puritan kind of mindset: "Poor/ill/mentally struggling people are poor/ill/struggling because they're Bad or Failing somehow, so therefore you should just eat grey porridge until you stop being a loser."
But it doesn't have to be like that. "Stuffing a few slices of deli meat or cheese in your wretched mouth while standing at the fridge" is a simple meal. So is a charcuterie board. It's substantially the same thing, but the vibes are different. I can tell you that I have gotten so much more joy and mental/emotional nourishment out of meals when I have taken a little extra time to make them beautiful and "fancy".
Eating ramen? Arrange your toppings like they do in nice ramen restaurants instead of just slopping them in any-which-way. Oh, and get yourself a really beautiful bowl to eat it in. This doesn't have to be expensive--keep an eye out at thrift stores or at the clearance section of stores that sell dishes. Every time you use the bowl, it adds a tiny little piece of beauty to your life, and over time those experiences of scraps of beauty (little moments of things that give you a grain of happiness) contribute to a much more positive and healthy mindset. If you get your hands on a bowl you love enough, then every time you use it will feel like a treat. Give yourself that treat as often as possible.
Eating a sandwich? Cut it diagonally. Why? I don't know, it's prettier that way, and it makes it a little bit nicer to eat. You could use a little ketchup or mustard or creamy sriracha to do those fancy dots/swirls/elegant smears on the plate like they do at really upscale restaurants. (The way you do the elegant smear is to put like half a teaspoon of your sauce or condiment in a little puddle, then use the back of a spoon to drag it out while rotating the plate. Ta da!)
Eating deli meat at the fridge? Get your beautiful plate (presumably you bought a beautiful plate when you bought the beautiful bowl, or use a clean wooden cutting board), and take an extra minute to arrange the meat and cheese nicely. Add a handful of baby carrots. Add a sprig of parsley or a dandelion flower that was growing outside your door, or a maple leaf. Add a spoonful of jam and some crackers. These are all cheap or free, and a charcuterie board is REALLY fast and low-effort to put together. But then you lounge on the couch and tell yourself, "This isn't depression food. This is Fancy. This is Special. Look how lavish and decadent I'm being right now." For me, my brain immediately perks up a little and goes, "Oh! Special treat! :)" Then I'm happy about the food, I'm smiling while I eat, and for a little time, I feel a bit better.
Oh, also: You're gonna buy a wine glass from the thrift store for a dollar and you're going to pour your can of Diet Coke into it. Or water. You're going to float your dandelion flower in the water. You're going to find a mug you adore and drink your tea/coffee out of your favorite special mug as often as possible.
You have to feed your soul. Beauty is a vitally important part of your daily nutritional intake. Don't skip it -- even if it feels silly and pretentious at first, over time it will start to teach your sad, tired, burned-out, weary, heavily-burdened heart that you deserve nice things, that there are small opportunities for precious tiny joys every day, and that the energy it takes to give yourself this supposedly-unnecessary little gift is a small investment for the amount of energy and pleasure it generates in return. I know folks who were straight-up suicidal who started doing things like this, and over the course of a few weeks or months, they realized that it had given them One Good Thing in their day that they could ALWAYS look forward to and to keep living for. This shit WORKS.
Bread and roses, friends: "Hearts starve as well as bodies: Give us bread, but give us roses too."