You can alter the price of a plan dynamically using CBSubs Promotions. To increase the price of a plan you use a negative promotion (e.g. -20 increases the price by 20). Promotions can come from fields as well. If the field is stored as a positive instead of negative value you can force it negative using the below usage.

The promotion is: A fixed amount
Fixed Discount Amount in currency above: -[FIELD_NAME]

Replace FIELD_NAME with the name of your field. This should increase the price of the plan by the amount of that field.

If the meals are just checkboxes or radio fields just create a negative promotion for each one then condition those promotions based off the field select. So for example if you have a checkbox field for sandwich (e.g. field name of cb_sandwich) and it costs $5 you'd have the below promotion.

Basic
Promotion Type: Applies to all purchases
The promotion is: A fixed amount
Fixed Discount Amount in currency above: -5
To which plans this promotion applies: YOUR_PLAN_HERE
Conditions
First condition: This condition:
Date A, Field A or Value A: Following CB field
CB Field A: cb_sandwich
Date B, Field B or Value B: Constant Value or String (CB substitutions can be used)
Value B: 1
Condition 1 (> for Dates): A = B (Value A is equal to Value B )

In this example the plan selected for YOUR_PLAN_HERE will have its priced increased by 5 if the cb_sandwich checkbox field is selected.

There's honestly about 4-5 different ways you can go about this. It sounds like the easiest approach is to just not have fields at all, but instead either subscription plans or merchandise plans for each of the items you intend to allow them to purchase then configure them to be non-exclusive so they can buy multiple plans at once (e.g. sandwich plan + chips plan). Otherwise you need to go the approach of altering a plans price dynamically using promotions like with the above example.