how to assign results from exec to variable

Question

How do I assign the results of an exec command to a variable. like the below, so when I do select @sql2 I get the result of the executed varchar sql.

declare @sql varchar(500)
declare @sql2 varchar(max)
set @sql = 'SELECT 
                PDB.OutletBrandID, OB.BrandName
            FROM 
                ProductDistributionBrand PDB
            INNER JOIN 
                [IND_roadchef].dbo.OutletBrands OB 
            ON 
                PDB.OutletBrandID = OB.OutletBrandID

            FOR XML PATH(''ProductDistributionBrandDetail''),ROOT(''ProductDistributionBrandDetails''),TYPE'    
--select @sql
set @sql2 = exec(@sql)  
select @sql2            

Answer 1

Use an output param:

declare @sql nvarchar(500)
declare @xml XML

set @sql = 'set @xml = (SELECT ..... FOR XML PATH(''ProductDistributionBrandDetail''),ROOT(''ProductDistributionBrandDetails''),TYPE)'    

EXEC sp_executesql @sql, N'@xml XML output', @xml = @xml OUTPUT

select @xml