If you've eaten lots of fibre it'll help you digest it and move it through your system, which will help with your losses - that said, if you're eating a lot of fruit and veg that's high in water as part of your SFree, you're probably getting enough.
It definitely doesn't hurt to try drinking a wee bit extra, anyway, it's easy enough to do (try filling a bottle up and refrigerating it, if you find it difficult)