The term "Mug Up" was used in coastal communities by the mid-1800s to describe any snack or coffee break throughout the day or evening.
“Mug ups" were an important part of life for fishermen. They would gather and have a hearty meal and warm up whenever they could take a break. Today, this nautical expression still describes a gathering of people for a drink and meal
Today, Mug-up is used by Scouts Canada to describe an evening snack (after dinner, but before Campfire). It is usually soup or hot chocolate and something to munch on (grilled cheese, etc).
We'll meet for a mug-up with the boys when we reach harbour.