Marland wrote:

When the FIL died we found quite a few tubes of steredent which
fortunately neither of us yet need for their intended purpose. When a
cup or mug begins to look a little grubby a tablet dropped in one and
left overnight brings it up clean.

From the MSDS, a decent mixture of cleaning agents ...

https://en.wikipedia.org/wiki/Potass...oxymonosulfate
https://en.wikipedia.org/wiki/Sodium_percarbonate
https://en.wikipedia.org/wiki/Citric_acid
https://en.wikipedia.org/wiki/Sodium_carbonate
https://en.wikipedia.org/wiki/Malic_acid
https://en.wikipedia.org/wiki/Alkylbenzene_sulfonates