Datatypes incompatible when concatenating variable

SET @d = GETDATE()
 

 SELECT @cid = [CustomerID]  FROM [dbo].[Customers] WHERE [CustomerName] LIKE '%' + @c +'%'
 
 SET @sql = 'INSERT INTO ' + @p + ' (AggregateName,TimeIndex,TotalSpace,UsedSpace,UsedPercent,DaysToFull,DailyGrowth,ControllerName,CustomerID)
                SELECT SUBSTRING(Aggregate,1,25), Cast(''' + CONVERT(NVARCHAR(10),@d,120) + ''' as Datetime) ,
                SUBSTRING(Total,1,15),
                SUBSTRING(Used,1,15),
                CONVERT(decimal(10,3),UsedPerc,3),
                CONVERT(int,DaysToFull),
                CONVERT(decimal(10,3),DailyGrowthRatePerc,3),
                SUBSTRING(Controller/Cluster,1,25),
                '''+@cid+''' FROM ' + @s
print @sql