Frequently do 100+ miles non stop, 2 water bottles on the bike, another 2 or 3 plastic 500ml bottles in my back pockets, which get used up first, crushed and dumped in a bin, and as much food etc that I can pack in my back pockets and small under saddle bag along with spare inner tube, mini tool etc. Sometimes I may use a musette if I think that I may need more fluids etc.
When your on your own, I feel theirs too many thieving scumbags about to be leaving your bike outside shops, carrying a heavy lock is not an option, so its careful planning required.