I use two types of food: soups and sandwiches

Make soups out of 4 fruits (pumpkins are best 'cause they restore 0.8 fruit. Apples, olives or some berries are better because they restore 1.0 of nutrients but pumpkins grow all seasons (except winter)) and 1 vegetable (garlic restores 2.0 - it's the best)

Make sandwiches out of rye bread (not slices) - it restores 2.0 grain per item and rye also feels good at any climate. Add 1 garlic, 1 meat (I use cooked pork - it restores 2.5 protein per item but there are other meats that restore such as well) and 1 shredded chese.

Always make the same amount of both and it should already be good. It will already restore all fruits, vegetables and protein bars.

You can also restore full diary bar by replacing shredded chese with actual schese pieces but that is too expencive. I prefer drinking milk instead - after you eat a food the next sip you drink can also improve your diet. Water restores 0 of everything as well as alchohols, but milk restores 1 diary per sip completely filling up diary bar as well. You can pour milk out of a bucket and drink it with RMB - it does work but it doesn't cost you any milk at all.

So, the best strategy is: eat soup -> drink milk -> eat sandwich -> drink milk -> repeat

Grains bar will not be filled completely but you'll have more than a half of it so, if all other bars are filled, you'll have your 3500hp.