a.Give him no more cake .
b.Don’t give him any more cake.
1.In these sentences, “cake” is in singular or plural?
2. we say " Give him no more cake" or “give him more no cake”?
We say “don’t give him any more cake” or “don’t give him more any cake”?
When you use the word cake as a countable noun ([color=blue]2.), then you are talking about whole cakes. “I baked three cakes for the party.”
The word cake can also be used as an uncountable noun ([color=blue]1.) and then it is used to talk about part of a cake: “a piece of cake”, “some cake”, etc.
So, your first sentence means “Don’t give him any additional pieces of cake.” Your second sentence means “Don’t give him any more entire cakes.”