As someone who loves to travel, visit friends and move about I often find myself sleeping on floors, kids' bunk, squeezy attics and generally awkward little spaces. I am also someone who (clearly) loves their yoga and can't live without a daily practice. I have had to navigate a lot of interesting spaces in my time and I would like to share a little of what I have learnt over the years.
The most important thing is to assess your situation first of all. Be realistic, if the ceilings are low; urva hasthasana is going to be a frustrating experience. if the floor space is narrow lying twists will need to be done with bent knees not straight legs. Work out what postures you can modify and which you should immediately put aside for a time when you have more physical space.
You will be able to practice in a way that suits your circumstances even if you don't have a mat and the floor is too slippery for ardho mukha svanasana.
I find it helps to make a bit of a plan, look for the elements you can incorporate into your practice and build around those. For example if you have enough space to separate your feet but not as wide as you need for trikonasana, think about a practice that builds up to parsvottanasana.
Begin by doing a few rounds of cat-cow to stretch out the spine, practice uttanasana to free up the lower back, uktakasana to build stability in the legs and gomukhasana to stretch open the shoulders. Then progress into parsvottanasana and wind down with malasana and baddha konasana. There are thousands of variations you can think up.
Standing one legged balances such as vrksasana are good to practice if you're staying in a room where the floor is strewn in lego, you can clasp your foot behind your back in natarajasana preparation to get a nice quadriceps stretch and preparation for back bend. Ustrasana can then be practiced using the hands to support the lumbar initially. Most spaces can accommodate child pose in some form.
If the ceiling is particularly low you could use it as a fulcrum for standing back bend as long as you don't crunch into the lumbar vertebrae you can lengthen and stretch the front of the spine deeper than without this support.
Walls are always wonderful to stretch against. Stand about a foot away from the wall and stretch arms overhead, place your hands onto the wall shoulder width apart and pull hips away from the wall causing the hands to slide down the wall, this way the whole mid line of the front body will elongate and the chest and shoulders can open without strain.
To finish a practice you need to work out whether you have enough space for savasana. A good alternative would be supta virasana followed by supta baddha konasana. A little longer than usual in a seated meditation will ensure you are able to cultivate that ultimate state of harmony. Try to make the best of these opportunities to explore your pranayama practices, for example nadi shodana (alternate nostril breathing)
I'd be happy to help you build a practice that suits you, contact me with any questions and good luck in yoga!