First thing you need to ask yourself about the sink is, do I "really" need it?
Can be a lot of work running water to it, running waste water away from it, and are you in a place were the water line(s) could freeze...
For the fridge, again would you really use it enough? If it sits out there in heat when you are not using it, it is an unnecessary expense unless you unplug it or turn it off when not in use.
If you have a large covered patio attached to your house, with the ODK there and you entertain right there a lot, then it might make sense.
I opted not to put either in the ODK as it is strictly used for cooking, not entertaining as it is away from house.
Our back patio (for entertaining) has a full size refrigerator we turn on day before we have guests, and turn back off after they leave.
Here is what I've done. I have the Memphis Elite as well.
https://pelletfan.com/index.php?topic=6014.msg60331#msg60331If you search the forum for Outdoor Kitchen or ODK, you should find several threads of builds people here have done.
Hope that helps some.
FYI- Add plenty of electrical outlets. Cheap to add and avoids "wishing I had one here" later.
And don't forget some storage for pellets.