But CloudKitchens is struggling to overcome early challenges, limiting how much it can take advantage of the crisis, at least in the U.S. Certain properties it has bought have turned out to be in worse shape than anticipated, making some of them unusable and sharply raising the costs of renovating others, say people with knowledge of the problems.

Several of these services offer premium subscription tiers that lead to free delivery and discounts. According to the Second Measure data in June, 17% of DoorDash's customers and 16% of Postmates' customers are subscribers, indicating lots of room to grow for frequent and loyal customers.

Most grocery stores have now begun to offer some form of their own in-house delivery, some of which are profitable. These profitable models generally have higher minimum order requirements, markups on items, non-flexible delivery windows (often multiple deliveries are pooled into one driver trip to save costs), and an unclear view into what product... See more