Backstory: I was in two craft stores over the weekend, Michaels and Hobby Lobby. I noticed a steady stream of people in and out as well as a large number of people holding paper coffee mugs. That got me thinking about higher end clothing stores with coffee shops (Nordstroms) and grocery stores with Starbucks (Harris Teeter).
The Idea: Portable Coffee Stand for high traffic retail shops.
Deep Dive: You would build a portable coffee stand, similar to a hotdog stand and work with a retailer to rent a small space inside or outside the store. You may have to go the food truck style route for health regulations but sitting outside a high traffic store should have similar effects.
Validation: Nordstroms (clothing) has coffee shops inside their stores.
Monetization: A physical consumer product, watch your margins. You may be able to partner with the retail store to offer some sort of joint discount.
Steps to Launch: You would definitely want to secure a spot before you do any building or thinking about the coffee stand itself. Ideally you would partner with a smaller, non chain retailer to prove out the concept.