Put some water to heat in a small pot and add the vinegar. Crack the egg inside a small bowl or cup. Once the water is simmering, make a circulating motion with a spatula inside the water and drop the egg in the middle of the spiral. Turn off the heat, cover for 6 minutes exactly. Take it out of the water once done.
Heat the olive oil in a frying pan and cook the breakfast sausage on medium- low heat on both sides until cooked through. Place the sausage on a plate. Add the fresh spinach to the frying pan with the leftover grease from the sausage. Cook until wilted and transfer to a plate. Cover with the poached egg.
Slice the avocado and put on the plate along with the cherry tomatoes.