A great way to meet Japanese girls(or boys)!
Apparently there's a whole bunch of guys who wouldn't mind sharing a morning coffee with Japanese females.
Our best-selling Japanese Wacky T-shirt ever features Japanese pick up line "Issho-ni yoake no koohii nomanai?" meaning "Shall we drink morning coffee together?" Saying this to someone of opposite sex would sound like you suggest spending a night together.
Read more on how to speak about sex in Japanese and how to avoid accidental misunderstandings