
How to not look like McDonald's guy.
Firstly, I really respect every job and the honest people who are doing it. So this is not complaining. Secondly I'm looking for non expensive things that will make a difference. Here is my thing.. I'm a pretty average looking guy.. height, skin color, dressing.. skinny which I think is the deciding factor between McD customers and McD staff. I have tried carrying fake glasses which worked sometimes. PS: this happens to me every now and then, not just McD.. small restaurants, shops, hotels.. by now I have learnt to laugh at it without resentment.

Happens with many people bro, you're not alone. Take it light and enjoy, maybe even serve one or two people to see their reactions 😂
On a serious note, get fit and bulky. That helps a lot.
Instead of other factors like height, color, etc., I think it largely depends on dressing.
Wear better quality and more stylish & colorful clothes than the uniform of a restaurant employee, and nobody will mistake you.
Otherwise, if you go to the restaurants wearing the same drab plain black or white shirt / t-shirt that looks similar to the restaurant employee uniform, then it's easy for anyone to make that mistake.