"applied coupons disable free shipping conditionally in woocommerce" Code Answer

The below code will enable "Free shipping" for applied coupons only if cart subtotal reaches a minimal amount (discounted including taxes):

add_filter( 'woocommerce_package_rates', 'coupons_removes_free_shipping', 10, 2 );
function coupons_removes_free_shipping( $rates, $package ){
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return $rates;

    $min_subtotal      = 250; // Minimal subtotal allowing free shipping
    
    // Get needed cart subtotals
    $subtotal_excl_tax = WC()->cart->get_subtotal();
    $subtotal_incl_tax = $subtotal_excl_tax + WC()->cart->get_subtotal_tax();
    $discount_excl_tax = WC()->cart->get_discount_total();
    $discount_incl_tax = $discount_total + WC()->cart->get_discount_tax();
    
    // Calculating the discounted subtotal including taxes
    $discounted_subtotal_incl_taxes = $subtotal_incl_tax - $discount_incl_tax;
    
    $applied_coupons   = WC()->cart->get_applied_coupons();

    if( sizeof($applied_coupons) > 0 && $discounted_subtotal_incl_taxes < $min_subtotal ){
        foreach ( $rates as $rate_key => $rate ){
            // Targeting "Free shipping"
            if( 'free_shipping' === $rate->method_id  ){
                unset($rates[$rate_key]);
            }
        }
    }
    return $rates;
}

Code goes in function.php file of your active child theme (or active theme). Tested and work.

Original answer:

The below code will remove "Free shipping" shipping methods when any coupon is applied without any settings need. There is some mistakes in your actual code. Try the following:

add_filter( 'woocommerce_package_rates', 'coupons_removes_free_shipping', 10, 2 );
function coupons_removes_free_shipping( $rates, $package ){
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return $rates;

    $applied_coupons = WC()->cart->get_applied_coupons();

    if( sizeof($applied_coupons) > 0 ){
        // Loop through shipping rates
        foreach ( $rates as $rate_key => $rate ){
            // Targeting "Free shipping" only
            if( 'free_shipping' === $rate->method_id  ){
                unset($rates[$rate_key]); // Removing current method
            }
        }
    }
    return $rates;
}

Code goes in function.php file of your active child theme (or active theme). Tested and works.