Beeswax
Beeswax is a daily spelling bee that only takes two minutes. You hear each word spoken aloud, spell it, and one wrong letter ends your run. The words start easy and get progressively harder. Everyone gets the same five words each day, and you can share your result.
I don’t play games on my phone, but I’ve been playing this one on my desktop. I’m not nearly as good a speller as I thought.