Only use water to re-hydrate yeast with. If you use a sugar solution the yeast get used to and adapt this and then wont ferment the more complicated sugars in wort (lazy buggers).
You've also probably heard about not just sprinkling yeast as it can lead to cell death. This happen because (iirc) the wort passes through te cell membranes too quickly and kills the cell. By making adding some malt extract to water you've made wort so will in effect be doing exactly the same as sprinkling.
From my reading on re-hydrating yeast your only supposed to use 10ml of water x Ygrams of yeast. Tbh I'm not sure why but thats what I do. Whether adding more water does anything I'm not sure
