Hi, we are a caterer, and we sell our catering by packages (sandwich lunch for 35 guests, 50 guests, 75 guests etc). We don’t identify to Shopify what is in the package. The package is just a product, and we have about 16 of them in total.
In addition we sell other extras to go with the package (product). However, there always must be a package in the sale. How can we enforce that there must be at least one product from the group of packages in the sale regardless of what else the customer ends up buying.
You could accomplish this by utilizing a product-add ons app. These apps allow you to display related products as add-on on the product page and cart page of your store. In this case, add-ons for your bundles. That way, you customer cannot purchase the products you want intended as an add-on as standalone products.
There is a great app called Easy Product Addons that is a great solution. They offer a 21-day free trial and is then $9.99/month afterward.
If there is anything else I can help you with, please let me know.