Azure SQL provides up to 200% of max provisioned database storage as backup and that also at no additional cost at all. However admins should be aware that there is a limitation according to the tier for the log size. eg for P1 it is 150GB.
I encourage admins to keep an eye on the log size by using below command. Some automation could be created to log this info in one SQL table every half an hour and finalize some alert on this table.
SELECT FILEPROPERTY (name, ‘SpaceUsed’)/128 UsedDBSize_MB
WHERE type_desc = ‘LOG’