I always kept thinking on stuff like...
What are other ways you can get spell slots then resting and magical items?
What's the point of cooking cept saving on rations?
Why put a restaurant with expensive food in the game if only go there for a plot point?
Why buy the Inn's food just so you won't starve?

You can litterly eat grass mechanicaly and be fine...
Now I am not suggesting a hunger system cause that would be painfull to track how much "hunger points" someone has.

Insted I recommend a food "recovery" system.

Warlock out of spell slots and has to short rest for the 3rd time in the dungeon? How about he takes abit of meat jerky they bought or someone with cooking skills cooked to recover 1 level 1 spell slot? Sure it takes em 30 seconds to consume it, so it's not good in battle... but atleast outside of battle they ain't resting everytime.

But not only that... Eating a big meal before a rest gives bonuses to players during the rest and waking up. Like maybe an extra die to recover more HP depending on the meal.

Now how do we make sure we don't have a guy carrying meals all the time and the wizard eating food every time to recover their 8th level spell slot?
"Fullness" 
Each meal will be identified on their "level" , the higher the level, the more full you get.

So the example for this is:
Take your wizard who has no spell slots left, Several level 1 and 2 slots, but only a single level 6 slot. And inbetween well.. let's not get too complex.

The wizard hasn't eaten any meals yet today. So they can decide.
Now let's say... each level spell slot is tied to what fullness level the wizard would obtain.
So if they eat food tha twill recover a level 6 slot.. they will gain 6 levels of fullness. So let's say their max is 8. So they can still gain 1 level spell slot or 2 level spells slots.
But wait.. there is more...
You can't cook a high level meal and then recover whatever spells slot, no you gotta cook the appriorate level food as well.
So you wanna gain that level 4 spell slot? It needs level 4 food.
This is how I would envision the Food can be used to recover spell slots out of battle.
Also naturally... the higher level the meal, the more time it takes to consume it.

So now to big meals give rest bonuses...well this one was come up with a friend during the discussion so the mechanics are kinda unknown at the moment.
But let's say everyone needs a short rest to recover, your party's cook makes everyone a big meal from the meat of the giant monster you slain. It comes out great and everyone eats it then takes a short rest to continune... now everyone heals alot more due to the meal. Some might even get an advantage or something? Eh.

So how do you decrease fullness? LONG RESTS reset it to 0 and each 2 hours after eating decreases it by 1 point. 
So if your fullness is 8, it would take 16 hours to digest all the food being awake.
But by taking the long rest, your body can easily digest everything in no time.
After all, we don't want food to replace long rests.

Now the last thing is how do we calculate fullness for a charater? I am not sure, might be constituation related, might be species related, might be size related, might be a trait. I haven't thought that out yet.

How do we calculate what level the food is with ingredients?
Or how do we know food has become "Rotten" and won't give an effect?
Won't it be alot of work to make items and recipes give effects?

Well I won't go with: "You need all ingredients and tools as well an oven to make a cake"
I don't want your potential chef player to be limited to recipes.

Insted we go with simple system wich goes like this:

- level 1 food: "condiment+"Any ingredient type or left-overs" (think jerky or salted left overs, a quick snack) or "Ingredient" + Cooking (Think things like a baked potato or cooking an apple) "Any fruit" (Since most fruits can be eaten as is) , Cooked food or salted food stay fresh longer.

- Level 2 food: Any stew contained: "Water+Ingredient+Condiment" or "2 ingredients" being cooked. Any salad containing: "1 herbs + 1 vegetable or 3 different fruits"

And from there it becomes "Add more different ingredients and types"
So yes all food items will have catagories under them. I think we should also have "Rare ingredients" wich will increase food in some way too and also "LEGENDARY INGREDIENTS" wich will naturally give big effects to your food or buff food to higher levels.

This will make cooking a fun mechanic for a player to do and help your party in many ways.
Or if there is no cook... maybe stop by that fancy restaurant for a good meal before taking a nap or go past a bakery to buy some food there.

Now this wasn't as refined as I think it should be and is just a "PROOF OF CONCEPT"
We all know spells like good berry will be used alot to for infinite berries, but it would only be limited to level 1 slots. Gotta have someone cook you up those berries to make them better.
But hey... let's discuss...
Would this be a fun system for players and DMs to do with food? Or will it add too much clutter and should be tossed aside? Should spell slots be recovered from a quick snack? 
DISCUSS AWAY! Cause... I am still abit new to making mechanics....

ADVENTURE ON!

First off, it's nice to see people thinking of ideas like this! I do think it would probably need pared down quite a bit in order to make it user-friendly. I like crunchy rules and everything, but this is a bit too in depth for D&D.  The development team has previously stated on several occasions they want to get away from being a simulation style game, and this is definitely borderline simulation. 

Also, the unearthed arcana section of the forums isn't meant for this type of post. The moderators will more than likely move this very quickly. The section you are in is meant for the unearthed arcana play test materials put out by the development team. 

Thanks someone told me to post it here....1st post, mods can remove it and move it..

No worries. Like I said, it's a good thought. And I am sure you will get feedback on it! The community on here is definitely vocal. 😁

It might have been a few year but id like you to know ive implemented something similair using salvage rules and im attempting to give modifiers to items that arent OP but are cool so this forum really helped thanks.

Don't tie concrete effects to concrete foods. Add some sort of "good life" tracker if you really have to, and have that grant inspiration/1/day resilience/spell slots, up to a maximum. Otherwise, "sure, he ate a nice stew, but I got a good massage! And jeff had both a stew and a massage!" And then you won't be playing DnD any more, you'll be playing quartermaster.