Hiten Bhavsar works around the lack of SQL Agent:
As we know, it’s crucial that you run Database maintenance regularly in order to keep your database performance up with the latest statistics and healthy indexes, here we provide another way to schedule this job using Azure Data Factory; this can be done on a scheduled time interval weekly/bi-weekly/monthly.
Click through for the process and try not to think too hard about this secretly being maintenance plans all over again.