Baking – Substitute baking containers

The short answer is yes; the longer answer depends on what kind of soy milk you're buying and how you plan to use it. I've used soy milk in my breads and cakes without noticing much of a difference in texture, but I use the unflavored, unsweetened versions of it (especially in cake-baking, as many recipes call for vanilla and some soy milks have vanilla in them). I avoid "light" soy milk when making creamy dishes or sauces because I want them to have the creamiest texture possible. If you're using soy milk in a soup or stew, don't allow it to boil because that can cause the "milk" to curdle (and add your acids at the end of cooking, also to avoid curdling). Oh, and be aware that some brands of soy milk are very sweet (you can buy it unsweetened, though); the sweetness might not work well in some dishes.

The most accurate substitution would simply be rum extract. It is concentrated rum with a huge kick of flavor, and much less alcohol. A little goes a long way.

If you're going to stick with a strong liquor my first choice would be a bourbon, it's a similarly "sweet" liquor that tastes good in baking. Another good option would be cachaça.

If you're avoiding liquor, then you may be able to use vanilla extract. Non-alcoholic varieties are available. According to Ochef you can also use molasses thinned with pineapple juice.

The rum is used simply for flavor.