Metformin.

Physical exercise.

One / two boiled egg per day.

GLP-1

There is no other 'one ingredient' for better health. Your body needs a multitude of ingredients for 'better health' (whatever that means to you).

Addition by subtraction. Delete junk. I am working on "the three C's". Chips, Chocolate and Cheese. The three are kind of addictive, and are way too easy snacks to grab.

You might say, a time lock on the fridge, though only cheese fits that solution.

Caffeine is the classic.

As others have said, the sugar without fiber is probably net bad for you and most of the things that benefit your life probably aren't dietary.

There is no greater thing you can do for your physical health and especially your mental health than be below 20% bodyfat, that becomes asymptotically true if you are obese.

If you lift then some form of protein, or potentially creatine.

> one ingredient to add to it

Reflection.

Journal about your previous day/make a plan for the day ahead.

That glass of orange juice has more sugar than a can of soda. Eat an orange, not the orange juice.

8 hours of sleep is one of the easiest ways to improve your health. It’ll improve your mental health, and also regulates hormones around cardiovascular health and weight.

If you add a few cups of water to the orange juice, it'll be much healthier. Because there would be no orange juice left, and thus way less sugar.

OJ isn't a health food, it's junk. Eat an orange if you must, or just drink water and pop a multivitamin if you're worried about that. But don't drink OJ. Certainly not every morning. Your gut and teeth will both be better off without it.

The supplements industry is mostly a sham. You don't need any fancy chemicals to function well. Just eat enough, but not too much, of a relatively balanced diet. Supplement it with a cheap multivitamin if you're worried. That's all you need. Get some exercise, minimize stress, and you'll be way healthier than any supplement addict.