What kind of Creatine and how much should I use for brain fog?

I have lots of brain fog lately, which is affecting my PhD a bit. It feels like I am always in that "right out of sleep" mode and can't think straight, even get lost in simple calculations.

I've heard that Creatine could help. I'm willing to try it out, but how much should I do (I don't work out and eat meat)? And which creatine (Creatine Monohydrate, Tri-Creatine Malate or Creatine HCL)?