ashfaqjan Support for multi-restaurant is limited in the core as to not bloat things up but features specific to use cases like yours can be added by easily extending the core. You can have a middleware within an extension that overrides the active theme based on the current user location (maybe an admin settings page to assign themes to locations). You'll then have something like this in your middleware handle() method
// Change the default theme when a frontend page is loaded and the user has a location set.
if (!App::runningInAdmin() AND Location::current()) {
params('default_themes.main', 'the_location_theme_code_from_the_settings_page');
}