Forgive me but I fail to see how this promotes the mass adoption of cryptocurrencies.
What Zeex does, if I understand it correctly, is help you convert your coins into a gift card,
which you can then use to buy coffee. It's more or less the same as converting your coins into fiat money
in order to buy coffee. If Starbucks really wanted to help promoting crypto, it could accept direct payments in crypto.
Earlier this years one of the Starbucks' CEOs said that he didn't  believe in Bitcoin.
That's enough of a hint to me as to what their position is.