A couple of quick tools, each built around one question rather than trying to cover everything at once. Pick whichever's actually relevant today.
Pick one drink, see what it actually costs to make, and try a few honest ways to grow the margin on it — price, speed, and waste.
Work backwards from the cost of a role to the minimum it would need to bring in — so you've got a number to weigh up, not just a gut feel.
See what a small, realistic lift in food-with-coffee sales would actually be worth, before deciding whether it's worth going after.