The recipe calls for almond milk and I think it's both a good and a bad thing. I'm not a huge fan of almond milk and I think it brings a weird flavour to all these smoothies. But it only as 35 calories compared to the 90 calories in skim milk. I stuck to almond milk just for that reason, but I got used to the taste after a while anyway.
You could also try coconut milk but that sits at about 60 calories per cup.
1 cup almond milk
1/4 cup ice
2 tbsp condensed milk
1 tbsp fresh lemon juice
Blend together all the ingredients and enjoy!