Coffee dispute: why does McDonald's VS Starbucks McDonald's sell coffee?

What do you think of a brand that is not a coffee attribute and suddenly sells coffee? Most of the reaction was strange, why did he sell coffee? Can he ever sell Starbucks? Maybe we all think it's impossible, but in fact, the brand has made a move in the market. A brand that does not sell coffee has launched a challenge to the core brand that sells coffee, and has led to the emergence of the other side.