I received this question recently:
Are there any canned lactose free evaporated or condensed milk products? If not, do you have a recipe on how to make lactose free evaporated and condensed milk?
The answer, sadly, is that there aren't any lactose-free evaporated or condensed milk products on the market. (Lactaid did a tryout of one in Puerto Rico, but has no plans to take it further.) Creative cooks will have to devise substitutes. No one-size-fits-all answer comes to mind, though. You'll definitely need to think about what you're cooking and what the role of the milk is in it.
First, what are evaporated and condensed milks? A good answer can be found at the Eating with Food Allergies site.
Evaporated milk is just concentrated milk (with about 60% of the water removed). For an easy substitute, use Vance's Foods DariFree Original Powder Gluten-Free Beverage. Rather than mixing it as milk, mix 1/2 c. of the powder with 1 c. of hot water. I used this substitute in this Dairy Free Fudge recipe.
Sweetened Condensed Milk
Sweetened condensed milk is just evaporated milk with sugar added. To make your own dairy free version, make 1 c. of evaporated milk (recipe above) and, over medium heat, dissolve 1-1/2 c. of granulated sugar in the mixture.
Vance's Foods DariFree is a potato starch-based nondairy milk substitute that is useful is many alternative recipes.
That's just the starting point. When people look for an evaporated milk substitute, pumpkin pie is often the target. I've given a couple of different possibilities for this in previous posts. One answer is tofu, as in Use Tofu to Substitute for Evaporated Milk. Plain soy milk will work if you boil it down to about two-thirds its original liquid content. You can also try just cooking a pie five to ten minutes longer to firm it better without boiling down the soy milk.
If you're looking for a generic substitute to use in many possible recipes, GoDairyFree has a maze of links that lead you to a variety of suggestions, from coconut milk to soy or rice milks.
And another range of possibilities emerge on this page at Celiac.com with plenty of cooks sharing their personal secrets.
You will have to do some experimenting to see which substitute works best with the particular dish or recipe you want to try. No easy answers, but a wealth of advice.