Finding cute things to say to a girl in the morning is of course an inherently different task depending on the nature of your relationship with her. If you are dating her, it is generally much easier to find something nice to say, as there tends to be very little (or even no) awkwardness, and you know her well enough to find plenty of things to talk about. However, even if you are dating her, there are still certain things you can say that will work very much in your favor. Telling her you had a lot of fun with her the previous night, and you love hanging out with her is a place to start.
Girls never love to be taken for granted, and by always telling them how much you appreciate their company you prevent that from happening. Secondly, you should try and find creative ways to tell her she looks beautiful. This can seem difficult if she’s wearing tattered pajamas, makeup is smeared on her face, her breath stinks, her hair is all over the place, etc. However, you have hopefully developed the ability to find all of this stuff endearing (after all, she is your girlfriend). Tell her you think she’s so beautiful when she just wakes up, when her eyes open for the first time, etc, and that you think it’s sexy when her hair is all disheveled. These types of cute things to say to a girl in the morning will make her feel special, attractive, and loved, and make her view you as sweet, charming, and irreplaceable.
If, on the other hand, you have woken up after a one night stand, your task of finding cute things to say to a girl in the morning becomes more difficult – if not inherently different. First off, you should acknowledge the night before “wow that was a fun night!” Try and get to talking about that to alleviate any awkwardness or guilt she might feel. The morning is not the best time for getting to know all about her.
Secondly, as stated above regarding a girlfriend, try and tell this girl she is beautiful. Tell her she’s even more beautiful in the daylight, how you didn’t really notice how gorgeous her eyes were, etc. Kiss her a lot, but don’t go further unless you can tell she wants it. Finally, try and make her laugh by making fun of your actions (and maybe hers) from the previous night. This has all been assuming you want to see the girl again. If you don’t, make it awkward and give her every opportunity to leave (she will take it).