Arg spent Christmas last year in rehab after his partying spiralled out of control and Lewis insists his TOWIE co-star is still on control.
Speaking to the Daily Star Online, Lewis said: "People jump to conclusions when they see him with a drink, but it was one drink at a toast.
"I think it shows more strength that Arg has been able to go out and have one drink with friends and call it a night, as opposed to coming off the rails."
Lewis admitted that having a drink in Marbs actually helped Arg to overcome another problem.
He continued: "I think the process of having that one drink has brought him back from feeling alienated and feeling human again."
Arg, 27, has impressed everyone with his recent transformation, swapping nights out for gym sessions, and Lewis confessed his friend has inspired him.
"I've seen what Arg has gone through with his training and his discipline so he's and inspiration.
"When we first had a conversation in the barber shop, when Arg first came back to the show, it really choked me up. Since then I've been thinking about myself and the way my life was going."