How do I track why my SQL Azure occupied space pulsates?
I'd have you look at tables and indexes with the following code:

SELECT sys.objects.name, SUM(reserved_page_count) * 8.0 / 1024 as [SizeinMB]
FROM sys.dm_db_partition_stats, sys.objects
WHERE sys.dm_db_partition_stats.object_id = sys.objects.object_id
GROUP BY sys.objects.name
ORDER BY [SizeinMB] DESC


You will want to check the size of the objects at regular intervals to see if you can determine which ones are in flux.