How Much Sauerkraut a Day
The traditional answer, which is also the practical one: a forkful with a meal. Two tablespoons, most days.
That is how fermented vegetables were eaten in the kitchens the habit comes from — a condiment beside the main thing, not a course and not a supplement. A 16 oz jar at that rate lasts one person about a week to ten days.
If you are starting from none. Begin with a tablespoon and give it a week or two before you increase. A large serving of any fermented food on the first day is a lot to ask of a system that is not used to it, and the usual result is that people decide fermented food does not agree with them when in fact the quantity did not.
Is more better? Not obviously, and there is a ceiling worth respecting: sauerkraut is salty by nature, because salt is what makes the ferment work. Eating a cup a day is a meaningful amount of sodium. Consistency over quantity is the useful frame here — a small amount often beats a large amount occasionally.
If you have a condition or a prescribed sodium limit, that conversation belongs with a doctor rather than with us.