When you get yourself a foaming soap dispenser you will see that it has a disclaimer on it regarding refilling the bottle.
Basically they say that you shouldn't do it to avoid clogging.
However they don't say that if you use regular hand soap you can refill it without problems.
So when you are out of soap in your bottle, go ahead and buy some more and refill it safely.
It is very easy to refill your dispenser, you only need to mix in a bit of air with the soap as it goes through the dispenser nozzle.
The reason why it usually clogs is because most of the soaps are quite thick.
To avoid clogging, add some water and now you're ready to refill.
To actually do the refilling process, fill up the unit with soap to about a fourth of the container size, then add water right up to about an inch from the container top.
Add the water rather slowly without filling it with suds which could overflow.
Next close the top so it's secure and start mixing it up by shaking it.
Shake it right until you see that all soap has safely dissolved in the bottle.
This way you not only use less amount of soap, but you also save on plastic and money at the same time.
And of course you save on water.
At first it might seem like some work to do and you'd be hard pressed to buy a new dispenser, however it's really easy and fast to do, it hardly takes a few minutes of your time and the savings that you achieve for yourself and the environment are worth the extra effort.
Some people actually add a bit of rubbing alcohol into the mix to make the soap even more antibacterial to fight germs off.
Of course, make sure first that you are not allergic to the rubbing alcohol.
If you want to add the alcohol, add one part soap, one part alcohol and two parts water to the mix.
Then shake well and you're good to go.