"I surely eat meat!"
Translation:Eu sigur că mănânc carne!
It's very similar to say that in English. Sometimes it is needed, sometimes not.
I cannot explain why sometimes we would add this că here, it mostly depends on context. What comes to my mind is that you would use it like here if someone has cast some doubt on whether you eat meat or not, so you say it like this to empathize the fact that you do.
Don't bother much with it.