Try to get more wears out of your clothes between washes. This helps with laundry but also with making your clothes last longer. Hang stuff up if you plan to wear it again instead of just tossing it into a pile on a chair (....everyone else also has The Chair for the not-dirty-but-not-clean clothes right?) and make sure it's not like jammed packed in a closet so it can air out a little. You can also spray with something like Febreeze or a wrinkle releaser when you hang it up so that the stuff has time to work before you need to wear the clothes again. A clothes steamer is also great for "refreshing" clothes that don't feel just washed but also aren't actually dirty and you can get a small portable one if space is an issue.

For professional/business attire, or things like jeans, change as soon as you get back home. For things like swimsuits or work out clothes, rinse them if they're really sweaty or dirty and then hang them up to dry. If you're just going to work out in something and get all sweaty in it again, it doesn't need to be super clean when you start as long as it's not like disgustingly smelly and you're going to change/shower soon. You can wash smaller items or more delicate items like bras, gym shorts, blouses, etc in the sink. Baby shampoo works well as detergent for more delicate things (silk, satin, other delicate fabrics) that aren't that dirty but you might need to try out some speciality detergents for hand washing to find something that doesn't feel like it leaves a residue without the rinsing power of a machine.

For things like underwear that you really want cleaner than what you're going to get with a quick sink wash, either buy more underwear ...or just wear underwear less.