Condensed milk is a thick, sweet, and rich dairy flavor commonly included in desserts, from puddings and pies to ice cream and candy (via The Kitchn). Sweetened condensed milk is simply a mixture of evaporated milk and sugar, and making a homemade one is quick and easy.
Making homemade condensed milk consists of adding 1 1/2 cups of sugar to 12 ounces of evaporated milk, bringing the mixture to a boil, and cooking until the sugar is dissolved and the mixture is slightly thickened (via Allrecipes). Another alternative is to mix a cup of nonfat dry milk powder with sugar, margarine, and boiling water (via Allrecipes).
Soy milk, rice milk, oat milk, coconut milk, almond milk, or cashew milk are great non-dairy alternatives. Just pour 2-1/2 to 3 cups into a small saucepan, and gently simmer the liquid, frequently stirring to prevent the bottom from scorching, until the liquid is reduced to about one cup, then add 2/3 to 3/4 cup white sugar.
Another alternative is cream of coconut is the way to go, made from coconut water instead of coconut milk, and it always contains an added sweetener. Cream of coconut is different from coconut cream, made like coconut milk (according to Spoon University) by simmering shredded coconut with water until the liquid separates into a thick and thin layer.