I have just decided on a whim that I no longer want to support the dairy industry and cut it out of my diet cold turkey. I've already trialed a run and I felt great but it was so difficult. Never realized how much dairy was in my diet in basically everything I ate and it wasn't long before I ran out of things to eat that didn't contain it. Even subjected myself to eating cereal with water which was extremely unpleasant. It's been hard but I know you're the community to ask for help because you've probably went through this sort of thing before.
You're gonna have to content to mostly making your own snacks I find. Popcorn kernels can be cheap and all you need to cook them is oil and salt/spices. As others mention there is plant based milk to try big fan of :soy-cutie:. Sussing out milk can be easy since it's a allergy it's often listed in bold at the bottom of the ingredients.