I'm not sure what you mean...are you talking about something that's not in the FitDay food database? If so, then what you do is make a custom food using the nutrition information from the shake and then add it to your food log.
There's not a lot to go on in your question, so I'm not sure if you are making the shake or using a prepackaged one. If you are making it, you can go to a recipe builder site and have the nutrition info created for you, then enter as a custom food; if you are using a prepared one, just copy the info from the label when you make your custom food.
Hope that answers your question. If not, let us know a little more specifically what you need!
And now that you don't have to be perfect, you can be good.