I'm usually honest and just say thanks for the invite but I don't fancy it. I'll lie in some circumstances but generally dislike lying to get out of things. I find lying about things like that is a bit pathetic really 🤷🏻♀️
I find it weird that people invent reasons to get out of doing things. I'd hate it if someone did that to me. I'd much rather people were straightforward and honest.
I've a great group of friends and saying you don't fancy attending something is perfectly acceptable.