[MoT3rror]

$DB_site was removed in vB 3.5 I believe.

You need to use $db or $vbulletin->db like this

PHP Code:

$vbulletin->db->query_write("
CREATE TABLE " . TABLE_PREFIX . "addon_table1 (
    addon_table1_ID int() NOT NULL AUTO_INCREMENT PRIMARY KEY,
    addon_table1_field1 varchar() NOT NULL,
    addon_table1_field2 varchar() NOT NULL
");

$db->query_write("
CREATE TABLE " . TABLE_PREFIX . "addon_table1 (
    addon_table1_ID int() NOT NULL AUTO_INCREMENT PRIMARY KEY,
    addon_table1_field1 varchar() NOT NULL,
    addon_table1_field2 varchar() NOT NULL
"); 


You can read about the db class here.

Also I believe you need to define the length of the int and varchar when making the column like this.
[sql]
CREATE TABLE " . TABLE_PREFIX . "addon_table1 (
addon_table1_ID int(50) NOT NULL AUTO_INCREMENT PRIMARY KEY,
addon_table1_field1 varchar(100) NOT NULL,
addon_table1_field2 varchar(100) NOT NULL
)
[/sql]

Just a suggestion, if you have phpmyadmin, you can export the table structure and it will give the query to make the table.