The afternoon seems to beg for something sweet. The right muesli already contains a decent amount of protein and fibre, but adding some non-fat milk increases protein by up to eight grams. Dairy is loaded with protein, potassium, calcium, and vitamin D, which muscles need to function properly.
After taking an afternoon walk, enjoy some muesli with non-fat milk (or Greek yoghurt) and fresh blueberries.
Total protein: 12 grams