I have a recipe that calls for low-sodium soy sauce but I only have regular soy sauce. I was wondering if I could just add water to the regular soy sauce.
I'm pretty sure it doesn't matter.
Low-sodium tastes a bit less salty and may or may not be healthier for you depending on whether or not reducing your salt-intake will benefit you personally. At most, perhaps use a little less, if you think the saltiness will be overpowering.
Depending on what you are making, I wouldn't add water. I never use low salt soy. You could just use a little less.