I have bought the tubs of butter cream from sams club twice before and loved it. but yesterday I bought a tub and it was to too thin much much too thin. Is it possable to add sugar to thicken it up? Or will that ruin it?

I noticed that now that the temp has jumped here almost 10 degrees from a few weeks ago, that my Sam's BC is also "thin". I whipped it for a short bit in the mixer and it seemed to help. I have also resorted to putting it in the fridge for a short period to help. They don't always keep that stuff in a friendly environment, ie in the backroom by the open bay doors, next to freezer exhaust fans, and it takes a long time for the entire bucket to come back down in temp, especially in the center. If you just bought it in the last day it may just be a result of where it was stored. Not sure if this will help but thought I would share.

I would just add some PS in the mixer with it. All buttercream is made of basically the same things. If it's too thin, adding PS should fix it.

I agree. Too thin add buttercream. Too thick add milk