In the miniature version of the crime scene, the mayo is shown to be Hellman's on the label, which is not available west of the Rockies, unless he had it shipped in, it is Best Foods west of the Rockies. The label of the mayo jar is not one of either brand however.
Joe says that he wanted to get drinks for Robert and himself. In the flashback scene, when he is searching for Robert, he has nothing in his hands. But he says that he spilled the drinks when he saw the dead body.