Apache 2.4 - how to use multiple files in files directive?

I can't find any info about it in the official documentation.

I try to allow access to two php files, A.php and B.php.

<Files "A.php">
    Require all granted
</Files>

<Files "B.php">
    Require all granted
</Files>

Does it work like this or is there a better solution?

Yes, it works like this. But you could also use a FilesMatch with a regular expression like:

<Directory /var/www/html/foobar>
    # deny access
    Require all denied

    # but allow for A.php, B.php
    <FilesMatch ^(A|B)\.php$>
        Require all granted
    </FilesMatch>

    # or alternative
    #<FilesMatch ^[AB]\.php$>
    #    Require all granted
    #</FilesMatch>
</Directory>