How to get sp_executesql result into a variable?

If you have OUTPUT parameters you can do

DECLARE @retval int   
DECLARE @sSQL nvarchar(500);
DECLARE @ParmDefinition nvarchar(500);

DECLARE @tablename nvarchar(50)  
SELECT @tablename = N'products'  

SELECT @sSQL = N'SELECT @retvalOUT = MAX(ID) FROM ' + @tablename;  
SET @ParmDefinition = N'@retvalOUT int OUTPUT';

EXEC sp_executesql @sSQL, @ParmDefinition, @retvalOUT=@retval OUTPUT;

SELECT @retval;

But if you don't, and can not modify the SP:

-- Assuming that your SP return 1 value
create table #temptable (ID int null)
insert into #temptable exec mysp 'Value1', 'Value2'
select * from #temptable

Not pretty, but works.

Here's something you can try

DECLARE  @SqlStatement  NVARCHAR(MAX) = ''
       ,@result     XML
       ,@DatabaseName  VARCHAR(100)
       ,@SchemaName    VARCHAR(10)
       ,@ObjectName    VARCHAR(200);

SELECT   @DatabaseName = 'some database'
       ,@SchemaName   = 'some schema'
       ,@ObjectName   = 'some object (Table/View)'

SET @SqlStatement = '
                    SELECT @result = CONVERT(XML,
                                            STUFF( ( SELECT *
                                                     FROM 
                                                       (
                                                          SELECT TOP(100) 
                                                          * 
                                                          FROM ' + QUOTENAME(@DatabaseName) +'.'+ QUOTENAME(@SchemaName) +'.' + QUOTENAME(@ObjectName) + '
                                                       ) AS A1 
                                                    FOR XML PATH(''row''), ELEMENTS, ROOT(''recordset'')
                                                 ), 1, 0, '''')
                                       )
                ';

EXEC sp_executesql @SqlStatement,N'@result XML OUTPUT', @result = @result OUTPUT;

SELECT DISTINCT
    QUOTENAME(r.value('fn:local-name(.)', 'VARCHAR(200)')) AS ColumnName
FROM @result.nodes('//recordset/*/*') AS records(r)
ORDER BY ColumnName

This worked for me:

DECLARE @SQL NVARCHAR(4000)

DECLARE @tbl Table (
    Id int,
    Account varchar(50),
    Amount int
) 

-- Lots of code to Create my dynamic sql statement

insert into @tbl EXEC sp_executesql @SQL

select * from @tbl