As a suggestion, don't use
'single quotes' for column aliases - it is not supported in certain scenarios, and makes it look like a string literal. If you need to quote column names (in this case you don't), use
[square brackets]. Also try to use table aliases to improve readability. If you reference those tables 10 times, we don't really need to see
CLM_BREAKFAST_TYPEA 10 times.
To be clear, the above is additional commentary meant to explain why the code sample below doesn't look exactly like yours. The following re-write of your expression does do exactly what your question asks.
,MealsTotal = COALESCE(NULLIF(CONVERT(VARCHAR(15),
COALESCE(A.MealsA, 0) +
... dbo.CLM_BREAKFAST_TYPEA AS A
... some kind of join
... dbo.CLM_BREAKFAST_TYPEB AS B