Use the INFORMATION_SCHEMA.TABLES view to get the list of tables. Generate Drop scripts in the select statement and drop it using Dynamic SQL:
DECLARE @sql NVARCHAR(max)=''
SELECT @sql += ' Drop table ' + QUOTENAME(TABLE_SCHEMA) + '.'+ QUOTENAME(TABLE_NAME) + '; '
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'BASE TABLE'
Exec Sp_executesql @sql
DECLARE @sql NVARCHAR(max)=''
SELECT @sql += ' Drop table ' + QUOTENAME(s.NAME) + '.' + QUOTENAME(t.NAME) + '; '
FROM sys.tables t
JOIN sys.schemas s
ON t.[schema_id] = s.[schema_id]
WHERE t.type = 'U'
Exec sp_executesql @sql
Note: If you have any foreign Keys defined between tables then first run the below query to disable all foreign keys present in your database.
EXEC sp_msforeachtable "ALTER TABLE ? NOCHECK CONSTRAINT all"
If you need to know more about SQL queries, it is recommended that you go for the SQL Certification Course.