Another approach:

Let's check for Friday, which is bit 7, I presume (I have no clue, check out in the Books online)

Bitmap is: 0000 0010

Integer value is: 2

AND the bitmap field with this integer value

Field & 2

Result is 2

If field is NOT friday, result will be zero.

Thus:

CASE WHEN Field|1=1 THEN 'Saturday'

        WHEN field|2=2 THEN 'Friday'

        ....

END

But still I recommend you to read the article, because a bitmap may contain different "1" bits. The CASE statement will see the first one and ignore the rest.