Here's a recipe to make your own:
TRAIL MILKSHAKE


1 x 100g powdered milk

3½ cups water

3-4 tablespoons chocolate sauce or caramel syrup

Sugar to taste (optional)


Dilute the powdered milk in the water, then pour the milk in a water bottle. Add the chocolate or caramel sauce and sugar. Then shake to mix all the ingredients.

Found on: http://www.hikingrecipes.co.cc/trailmilkshake.php