The Scarab God's ability exiles a Clone from the graveyard. The Clone copies a Grizzly Bears on the battlefield. What are the characteristics of the token?

The token will end up the same as a normal token copy of Grizzly Bears: a 2/2 green Bear creature.

The Scarab God's ability includes modifications to the copy effect it creates, and these modifications become part of the token's copiable values as part of applying that effect, so the token copy of Clone that it's initially making would look like this:

Clone - {3}{U} (Black)
Creature - Zombie
You may have Clone enter the battlefield as a copy of any creature on the battlefield.
4/4

…But this creature has a replacement ability that modifies how it enters the battlefield. You apply that ability and choose to copy Grizzly Bears, so now you take the Bear's copiable values and apply them to the token, overwriting the existing characteristics. The Clone ability doesn't include any exceptions or modifications to the copy effect it creates, so it copies all the Bears' characteristics, and you get:

Grizzly Bears - {1}{G} (Green)
Creature - Bear
2/2