What is the best milk substitute for a cake mix? I've looked online and it keeps telling me different things.

it tells you different things because there are so many good choices -- almond milk, soy milk, cashew milk -- those are all good choices -- some people use coconut milk -- you can use water, tea, coffee, koolaid, jello, melted non-dairy ice cream, melted sorbet, coulis -- there's 10,000 best milk substitutes -- fruit curds, non-dairy sour cream, beer, wine, applesauce, etc.

the best one is the one you like best -- since it seems you're just starting out on this idea then enjoy the ride and start testing --

do you have a particular cake flavor you want to make?

Just like memphis said; it all depends on the flavor of your cake. For example: you can substitute milk with water, if you're making a dark chocolate cake, using dark cocoa powder. You can also substitute milk with orange juice, if you're making an orange flavored cake; or with lemon juice if you're making a lemon flavored cake...etc.

My favorite is without a doubt coconut milk ( I use the milk not the cream) - it leaves the cake with such a soft, moist, bouncy texture and I find for most cakes the flavour is very subtle so barely noticeable. I had to try a few of these when my little one was younger as she was really sensitive to dairy (including any dairy that I ate). I hated water and found that it left the cakes dry. I found orange juice worked to a point but generally left the cake really sticky on the outside, which you can get around if you are of course covering it. I found that soy milk/almond milk/ coconut milk (home made for the coconut milk) etc gave a reasonable result, not as dry as using plain water but not as nice as of you were using dairy. Everyone will have different opinions of course depending on what they like but that was my experience with the substitutes that I tried.

Can't get back to edit my post but I just realised that I didn't write that the coconut milk that I liked was the tinned version and the one I didn't like was the home made - I found that they gave very different results.

The tinned or canned coconut milk contains the fat of the coconut. When you say homemade, I'm guessing you boiled or seeped the coconut meat and drained off the fluid- while I love this stuff, it doesn't have much oomph. I use soy in all of my baked goods. The white and chocolate cake recipes I use call for curdling the soy with apple cider vinegar (1tsp acv to 1 cup soy). The cakes are always rich and super moist. Those used to dairy are normally shocked to learn the cake is dairy free.

@yummy -- some of the best cupcakes i've ever had were vegan -- yes i was shocked

 I admit- I was shocked the first time I had vegan cake!

I found this page: non-dairy-milk-guide-for-all-your-cooking-and-baking-needs, it gives the low down on all dairy milk alternatives. Hope @KTcakedesign you find it helpful!

"In baking, soy milk is also one of the best choices because of its high protein content. According to veganbaking.net curdling milk with an acid such as vinegar creates complex flavors and thickens the mixture. This in turn “increases leavening power and enhances the crumb quality of cakes and muffins.” Since curdling is dependent on protein content, soy milk does the best job."