Other mistake: Torey Martin says that he had an accident 5 months before, but the car crash evaluation is signed 31/07/2016. Not only it was a Sunday - unlikely day for the car shop to be working -, but that would put the events of the episode on January, contradicting the bank statements and what was established in previous episodes.
Plot hole: The big climax of the episode involves Humphrey arriving at 1 PM to escort Martha to the airport as he promised, finding the shack empty with a parting letter from her and rushing on Dwayne's motorbike to catch her plane, failing to do so. All very cinematic, but that means that had Martha not left early, she could have not caught the plane at all.
Character mistake: Florence says that Commissioner Selwyn Patterson and Martha are halfway through the bottle, but the bottle is practically empty. (00:29:55)
Continuity mistake: Evening at Humphrey's; Goodman and the two French main characters are looking at the unlikely pair of the Commissioner and Martha being drinking buddies. Florence is looking over her left shoulder in a pinup pose, but she is turned right in the reverse shot. (00:29:45)
Other mistake: In the bank statement that Dwayne hands to the DI, there are cash withdrawals "from the past three months", with the past three months being January, February and...February, again. (00:20:30)
Continuity mistake: Goodman rushes out of the police station after spying someone tampering with the jeep. First time we see the various market stalls in front of the station, and two women are moving from one stall to another; one of them is wearing a sleeveless pink dress and has her hair in a bun. Humphrey arrives by the jeep in the next shot, and the two are back to the same stall they departed from earlier. (00:17:35)
Continuity mistake: This is one of those episodes where names of the suspects on the whiteboard they look different under different angles. The horizontal stroke of the J in "Jerome Martin" is touching the hook, or not, the B in "Sabrina Martin" is different, etc. (00:13:15)
Continuity mistake: Florence spots the camera inside the cricket club's bar and points at it as she goes to fetch it. Points with her right hand, becoming the left hand at the cut. (00:11:20)
Continuity mistake: Opening; a creepy dude puts his hand on the shoulder of the hero of the cricket game. In close-ups the hand is not on the polo's neck, in the intermediate wide shot it is right on it. (00:02:55)
Answer: Most likely they had only tropical exotic drinks, he wanted an old fashioned English beer.