What does it mean to call someone "sauce" in Japanese?

I think the explanation upstairs is not thorough enough.

Mainly in two aspects. The first aspect reflects the intimate relationship between the speaker and the object of expression. For example, if the landlord is a girl, then the landlord can call her XX sauce for the sister who is very close to you in the dormitory, but not for the girl who is only in one class. Of course, boys don't use XX sauce. Otherwise, they will hold on to it.

The second aspect is that it also reflects the speaker's own "sister attribute" and "weak attribute", which means coquetry. An obvious example is that no matter what cartoons or whatever, only brothers and sisters will say "Oh, Ni sauce" (brother) and "Oh, that sauce" (sister), while brothers and sisters call their brothers and sisters by their first names.