Just "more one"

My friend and I were at a bar, and he inquired me:

B: Do you want to drink more?

Then, I confidently answered:

J: Just more one.

He started laughing at me. I looked at him with a question mark in my expression. I knew I said something wrong, but I didn't understand which mistake was. So, he corrected me:

B: You should say "just one more".

Well, this mistake happened many times. All the time that I was trying to say "one more", "two more", etc I used to say in the wrong way. Now, when I was writing the title of this post, it was really weird to me write in this way (Thanks God, and my bully friend). But, I've seen many Brazilians doing the same error. Why does it happen? Because in Portuguese we say "mais uma", that literally means "more one". My friend used to bully me all the time, so I learned!