Kid Version of a Milk Shake: No Blender Needed

This recipe comes from my daughter, Aviana, who found it in book about "how to do everything better." A milk shake - no blender needed.

1 small plastic zip-loc bag
1 large plastic zip-loc bag
1 cup of milk
1 tablespoon of sugar
a couple of drops of vanilla extract
ice (and rock salt if you have it)

Pour milk, sugar and vanilla in the small bag, seal and shake gently. Fill the large bag half-way with ice and sprinkle with rock salt (optional). Put sealed small bag in the bag of ice. Seal and go outside and shake it for 5 minutes. Pour contents of small bag into a glass and enjoy!