They do: http://www.amazon.com/TOMLYN-PRODUCTS-Nutri-4-25oz-tube/dp/B...

It's intended for dogs and cats. I don't think you'd enjoy the taste.

You could always buy some Compleat or other tube feeding formula. I can't imagine it would taste good, but it is what you asked for.

http://www.novartisnutrition.com/us/productDetail?id=91&...

Not bad, but I've learned that when they don't list the price you usually can't afford it.

Yes, it's called a banana.