Like I promised, I changed the last universal developer recipe like this:
800 ml water
3 g Potassium Metabisulfite
6 g CD4 (color developer for C-41)
30 g Soluble coffee
35 g Potassium Carbonate
1,5 g Potassium Bromide
Water to make 1 Liter
I developed for 12 minutes with constant agitation at room temperature, bleached and fixed. Perhaps I could have done 15 minutes too, the results would not be so different, I think.
Because coffee is acidic I raised slightly the Potassium Carbonate content and I got evidently better negatives and the difference can be appreciated by sight.
One of the 8 photos made with an Agfa Clack and expired Fujicolor Superia 100: