While it is true that there is no DROP ALL TABLES command you can use the following set of commands.
PRAGMA writable_schema = 1;
delete from sqlite_master where type in ('table', 'index', 'trigger');
PRAGMA writable_schema = 0;
you then want to recover the deleted space with
and a good test to make sure everything is ok
Note: These commands have the potential to corrupt your database, so make sure you have a backup