well, don't ask them, they won't be able to tell you.
Model it for them.
So, I want a banana, bananas have run out. throws themselves on the floor.
You model for them. (well, when they aren't screaming)
I'm sorry there are no bananas. You wanted one and it made you sad that there weren't any. It made you feel cross inside.
Accidentally knocked over something they have made/built.
You model - you spent ages building that tower and no it is broken. That is frustrating isn't it, it makes you feel cross because you spent so much time making it. .
Acknowledge feelings. Helping them to verbalise feelings, sitting with them while they express feelings.
On the other hand, it is fine for them to feel angry and when they are angry, if they want to shout and drum their heels on the floor, fine. But you don;t have to sit there, you can leave them to it, and say - when you are ready, I'll be in the kitchen, - and walk away and let them finish having a tantrum, and then when they are ready they will come and find you