I just recently had this same problem with my boys.
I thought they were just eating way too quickly, but it started happening more and more frequently recently.

I went to the vet and he said that he thinks they might have hair balls.
I said that I didn't think that was it because Ive seen what a hair ball looks like, (my mom has a Calico and she throws up hair balls sometimes- but they look different- filled with cat hair- and this doesnt look anything like that) I explained that their throw up looks like un-chewed food, no hair or anything else. The vet said sometimes cats get a ball of hair stuck in their bellies, especially when they shed more in the summer months. If there is a hair ball inside, it in turn can block the food from being digested properly, and they will automatically throw up their food.

He gave me some Petromalt for them to talk daily for 5 days, and then once a week (its a gel that is kinda liquidy and smells like syrup) He said it should solve the problem.

It's worth a shot! I'll let you know if it works, but in the meantime, maybe switch to or mix in some hair ball dry food to their diet?

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