It would not be harmful to your non-diabetic cat if it drank some of the water, but I prefer to add it to some canned food so that one can have a better idea if the intended cat has gotten the entire dose.
In the cat there are factors that help them to respond well to therapy. It is important to feed wet cat food and no dry food at all if possible and all foods including treats should consist of ingredients suitable for a diabetic. In addition I give digestive enzymes, probiotics, and fish oil. Dia-IonX helps the body to better utilize the diet and supplements better for a synergistic effect for faster healing. It is also important to avoid giving water that contains chlorine and fluoride.
Please let us know how you do or if you have any other questions.