Here is my Prima Facia observation.
You may want to look at the Business problem that you are solving, wether it has a Business potential. Specific to Coffee deliver here are some of the thoughts.
In US and Europe in some of the busy cities, there is a queue for Coffee for folks going to offices in the morning. You may want to look at having a Coffee Bot that people can order 5 mins before they reach the Coffee shop and the Bot is ready to deliver the Coffee when they arrive at the Coffee shop.
For people working in the office, if they can order the Coffee from their desk, the Bot picks up the Coffee and delivers the Coffee at their desk. That would mean a lot of sophistication in the Robot.
However that sophistication, you can probably look at areas where there is a larger Business need. Eg: Logistics where you can use Robots for Order fulfillment in Warehouses. One of the fastest growing Startup in India Grey Orange does that. They have raised Series B funding as well.