coca cola will contact them, but that won't necessaruily result in a chage. As pointed out, drones are a distinct market from sugary drinks, sot he likelihood of consumer confusion is low. It's true that Coke's legal department will write a grumpy letter anyway, in order to create a legal record of actively defending their existing mark, which can be raised in court if they are ever confronted with a genuine infringer.
I assume/hope the Spirte team have budgeted a few $ for the legal expenses in replying to such a letter, but agree with the poster below that the cost might well be covered by the value of free publicity over a trademark dispute. I hope that's not a deliberate strategy, as it's the sort of thing that could turn into an abusive practice.
If you had clicked the link I provided, you might come to understand that since 1995, U.S. trademark law does not just work in the way you described, but also includes the concept of "dilution", where famous marks are protected by law even though there is zero chance of consumer confusion.
You should be looking at the Trademark dilution revision act of 2006 which has superseded it. While Coke would easily get an injunction against blurring, there are counter arguments about similarity, and the lack of intentional or factual associations with the famous Sprite mark, not to mention it's lack of inherent distinctiveness (as opposed to say '7up'.) The situation is more nuanced than you suggest.
I assume/hope the Spirte team have budgeted a few $ for the legal expenses in replying to such a letter, but agree with the poster below that the cost might well be covered by the value of free publicity over a trademark dispute. I hope that's not a deliberate strategy, as it's the sort of thing that could turn into an abusive practice.