Out of milk?

Any dairy or dairy like product can be used in baking. Non dairy coffee creamer, mixed with water (try one part creamer and 3 parts water), ice cream (thaw first and cut back on sugar), cream or half and half (add three times as much water as cream). Use potato water in bread instead of milk.

Sour cream

If you need sour cream for a recipe, you can substitute cottage cheese, pureed, or mashed thoroughly. Plain yogurt will do the trick, too, but it may be thinner.