Is this a theoretical project for school, or are you actually trying to automate the role of tea boy ? Is your system designed to work on a single building or campus, or are you designing a vending machine system to be widely distributed in public ?
The most complex and difficult part of the system you describe is the payment processing, followed by the user interface. The batch management and actual machine automation are simple by comparison.
A custom smartphone app or web portal with menu and shopping-cart functionality, tied to one or more micropayment processors, is the sort of thing that you should outsource to a professional development company or buy an off-the-shelf solution used by restaurants in your area.
In my area, I can think of several. All the food delivery services have one that sends orders to an Android or iOS system or an e-mail address. DoorDash, Uber Eats, Postmates, and Grubhub dominate the US market, while smaller platforms include BeyondMenu and ChowNow. I admit I have no idea what companies are popular in your part of India.
In my opinion, a custom mobile app is not the right solution for what you describe, at least not in a limited deployment area. Survey your proposed customers and find out what apps they use to order takeout food on their smartphones.