In JEI the recipe for sugar calls for 5 Canes and 600mb of water to make 1 piece of sugar, but when you actually do it you get 5 sugar instead. Which recipe is supposed to be the correct one?

Tested and the correct amount (1) is outputted.

Are you playing a modpack that perhaps modified the recipe?

I'm playing 170 with no modpack.

Here's the recipe in jei which is like what you're getting

this is what I get with 15 sugar cane and a full barrel of water

Confirmed, this will only occur when there are more than 1 set of inputs.

It also consumes the required amount of liquid per item in the stack.