Don't underestimate the size of our ships, a Cobra MkIII is 28m long and wider than that, compare this to something like a Learjet 45 which is equipped with all the mod-cons for 9 passengers at just 18m long.
I mean even a sidewinder can carry 8 tonnes of cargo with shields, 8 tonnes! that's like 8 average size cars.
In my mind, something like a Sidewinder, Eagle or Viper would have facilities akin to those on the ISS (basically a sleeping bag you strap yourself into to sleep, and a vacuum tube for other requirements), Haulers and Adders have something like a basic bunk and a airliner toilet, the Cobra and maybe Vulture have something like the cabin you'd get on a submarine, the Asp a cabin like those on a Naval warship, and the bigger ships proper cabins. When you get to things like the Anaconda, Vette or Cutter they have entire staterooms (the Cutter will have a pool, and the Vette a gym as well