Yes - however there are pros and cons. Below are some processes for your considerations.

a) On the website, customers would see multiple 'outlets', each with a different set of food menu. 

Pros: User traffic from respective social media platforms could be consolidated to one URL, with additional benefits of saving costs.

Cons: Customers may get confused with affiliated brands.

b) To manage sales orders, we could create two sets of cashier logins. Each brand's cashiers can only access their own sales orders and menu.

Pros: If there’s a finance person  to oversee the orders from all brands, it’s  easier to just refer to one website, instead of two. 

Cons: HQ team would be able to view and manage food menus from all brands,  Making it more complex for less savvy users. 

c) Voucher code issuance for promotional use and refund requests.

Pros: We could restrict voucher usage for a specific branch/ brand so Brand A vouchers can only be used for checking out on Brand A branch.

Cons: We experience with other merchants that combine multiple brands in a single website: the consumer couldn't be able to comprehend. 
    
Example: Consumers see FB posts with promo code. Consumers click on the post, land on order site, they would expect the same promo code is applicable for both brands. They usually report website errors if they can't checkout using Brand A promo code on Brand B branch. Sometimes they would drop a bad review for this kind of "errors". To resolve this, if we need to run a promo on Brand A, we ought to apply the same promo on Brand B too. 

d) Menu | We could separate the menu by branch so we could have it separated after consumers have chosen a branch/ brand.

Cons: For HQ backend, users can't filter the menu by outlets so there would be a long list of food menus to choose and manage. 

e) Technical | Website analytics and conversion tracking

Cons: We could only have one FB Pixel and Google analytics per website. It would restrict the flexibility to pinpoint specific ads conversion and we might confuse FB lookalike audience algorithm.

It could be harder to target the correct crowd for the reason above.