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The Jersey Shore legend failed to endorse a metabolising substance by an organisation called Performance Brand, according to TMZ.
Legal documents reportedly reveal that Sorrentino was paid an advance of $75,000 for the promotion work.
Sorrentino had a stint in rehab earlier this year to deal with a "prescription medication problem" and alcohol dependency, which coincided with his marketing work.
Performance Brand say that his failure to share with them his drug addiction was a breach of contract.
The Situation has apparently launched a counter suit against Performance Brand, arguing that the company failed to disclose a marketing plan.
The reality TV star, 30, has been sued before over similar circumstances.
