soymilk

Dear bakers,

So many  of the wonderful bread recipes we use call for milk, buttermilk, butter, etc.   Have you found any good substitutes for any of these ingredients?  Specifically, would soymilk be a good substitute for milk or would some other food be a substitute for sour cream, for example?  Could cocounut or rice milk be used?  Any suggestions for butter substitute?  This all concerns those of our "customers" (aka family guinea pigs) who are allergic to dairy).

Please advise