Selected 6

import 'package:flutter/material.dart';
import 'package:gap/gap.dart';

final selectedTopping = [];
final listTopping = [
  'Tomato',
  'Soyu',
  'Sledri',
  'Coconut Sprey',
  'Mayonaise',
];

Column(
  crossAxisAlignment: CrossAxisAlignment.start,
  children: [
    const Padding(
      padding: EdgeInsets.symmetric(horizontal: 16),
      child: Text(
        'Topping:',
        style: TextStyle(
          fontWeight: FontWeight.bold,
          fontSize: 14,
        ),
      ),
    ),
    const Gap(10),
    ...listTopping.map((e) {
      return CheckboxListTile(
        value: selectedTopping.contains(e),
        onChanged: (check) {
          if (check == null) return;
          if (check) {
            selectedTopping.add(e);
          } else {
            selectedTopping.remove(e);
          }
          print(selectedTopping);
          setState(() {});
        },
        title: Text(
          e,
          style: const TextStyle(
            fontWeight: FontWeight.w400,
            fontSize: 14,
          ),
        ),
        controlAffinity: ListTileControlAffinity.trailing,
        contentPadding: const EdgeInsets.only(left: 16, right: 10),
        dense: true,
        visualDensity: const VisualDensity(
          horizontal: VisualDensity.minimumDensity,
          vertical: VisualDensity.minimumDensity,
        ),
      );
    }),
  ],
),