The LD50's for a 100kg person of salt (100g), sugar (1kg) or vitamin C (1.1 kg) are huge. Long-term exposure to sugar can affect your overall health, like causing insulin resistance or just being processed into fat. Salt isn't bad for you, unless you already have a heart or kidney problem. Vitamin C might have some side effects but the evidence is very thin so far.
Wait, are you really arguing that it's impossible to have too much of something that is water-soluble? What about sugar? What about salt?