@Droite
Does he manage to avoid these tantrums at work? If so, how come he chooses not to control them on holiday?
One point of view: it will probably be harder to control them on holiday, where everything has high expectations of enjoyment attached to it, but is also totally unfamiliar and possibly less controlled. At work, there will be a different dynamic that he has had enough practice with to handle things and know it works a lot of the time.
It's interesting to say 'He should work out coping strategies'. I think this sequence resulted in an unpleasant and clumsy dump on another person, but possibly there are a couple of coping attempts that you could argue were intended here. He needed to eat (may have been stressed about breakfast hours finishing and the option being taken off the table for example) and could have headed off the big out-of-control reaction by doing this. He may be finding it pretty difficult to be in only 1 room and bathroom with more people than usual, not a house with his own stuff and withdrawal opportunities.
He probably walked out most of his anger and agitation to try to get back in control of his stress, but this looked like a storm out with an 'are you ever coming back' element. The cafe will probably have tested the ground he might have gained on the stress control front.
I am sorry that his behaviour was so erratic but I think he may have had intentions that looked reasonable to him (and preferable to the alternative for him, which would have been a major ASD overwhelm and shut down when he realised he wasn't processing anything - something I recognize very well, that can't just be fixed and has to keep 'loading' in its own sweet time).
He definitely does need some support from someone who is skilled in this - get a recommendation if you can. He may be able to come to the point of expanding his point of view - 'How would OP interpret it if you stormed out while she was in the shower with no warning?'