Philosophydaddy, you will need to bring your own water, since you will want to be self reliant, but that said, there was ample water at the last one I attended.
There will be an HQ with a safe zone set up for re-whatever, including sleep, but it is entirely up to the individual squad as to how much time is spent there. The ideal is to only go back when you REDCON out from casualties, grab ammo, water and snacks then head out again with what you will need for the next few hours. We ended up holding down some buildings and rotating watch/patrols and dozing for a few hours, but other guys went back and racked out, while others went all night long.
As far as loadout goes, lighter is better. Having learned a thing or two last time I will be packing ammo, water, electrolyte and/or energy chews, jerky/trail mix. I'll have a gear bag back at HQ with fresh socks, gold bond, warmer clothes, a meal or two and spare gear etc.
