The phrase "full cup" means that someone or something has reached their limit or capacity.
Sentences with «full cup»
I wanted to see a half full cup of coffee with a folded up newspaper on the coffee table to let me know real people live here. (theinspiredroom.net)
If you want to up the peanut butter flavor, you can get away with adding up to one full cup without altering any of the other ingredient measurements. (ohladycakes.com)
I used 2 full cups finely shredded carrots, 1/2 cup golden raisins and 1/2 cup diced dry pineapple. (elanaspantry.com)