With temperatures over 30 °C / 86 °F, like we have here, at the end of the day not everything you wore that day will smell that fresh anymore.
Not only will it save you money, in some cases one would prefer to wash smaller items like underwear or T-shirts by hand rather than give it to the front desk staff for laundry services.
The problem in hotel rooms is that the tap water is not always hot enough. If you let things soak for a while, the water will quickly cool down, making this method less effective.
The only other way is to wring wash it with soap under running tap water.
However, if you have a plastic bin eg. the garbage bin, if it’s clean enough or if there’s an AC outlet nearby the sink, a travel immersion heater can be of great help for soak washing. Actually due to the capacity of the heater (300 Watt) and the larger amount of water, it will never reach the point of boiling, but more like 60-70 °C / 140-158 °F, which is good enough to dissolve most stains.
Although real washing soap would be better, I use shampoo or body soap.
Let your items soak for at least 30 min’s and then wring it out under running tap water.
To prevent your next coffee or tea has a dirty soap water taste as well as removing limescale from the spiral, make everything spic-and-span by cleaning the heater element with eg. the hotel’s toothbrush and toothpaste.