I think you can use "how many" if you are using sugar packets!
How many sugars is difficult because it assumes that the spoons of sugar or cubes, will be uniform. Of course they are not!
If the question "How much sugar do you want in your coffee?" is asked; the reply could be specific so all is understood.
NB I'm currently reading about nutrition - best to stay away from sugar!!!
Who puts sugar cubes in their coffee, these days?
Surely "Would you like sugar with your coffee?" would be more polite
Sugar is uncountable.
sugar was uncountable in the past.but now we can count it:S
It really all depends on the situation... if sugar cubes are being used then how many sugars would be somewhat acceptable, although it's still not considered proper English. However, the more polite* and appropriate of the two is "How much sugar do you want in your coffee?"
*It would even more polite if the sentence were "How much sugar would you like in your coffee?"