1 portion

1 cup of watercress
1 cucumber in pieces
½ green apple in pieces
1 lemon juice
½ glass of water

Mix all the ingredients in a blender and enjoy immediately.

Cal: 77.7         P: 2.1         F: 0          Cb: 18.4

You can replace it with a fruit or fruit portion, if you have fruit in your plan. Or for an integral bread or rice biscuit, if you have bread or cookie in your plan.
If you don't want to use it as a replacement, you can add it to your plan without replacing anything, one day of the week in your snack or lunch.