I am sorry to say that watching the whole of the press conference with President Trump does not provide any reason to think that he did not mean direct injection. Don't get me wrong, he may not have meant direct injection . . . possibly he meant using a disinfectant lung lavage (ie a lung bath) or some such. Lung lavage (using a saline solution) is sometimes used to remove contaminants or biological substances that build up in the lungs and result in difficulty breathing. There are two problems with this idea.
One problem is that although saline lung lavage has been used to treat lung disease symptoms (ie DIP and PAP), it has no known effect on the underlying pathogenic or genetic cause.
Another problem is that a lung lavage using disinfectant is not the same as a lung lavage using saline solution. Any type of disinfectant that is capable of killing a virus (ie alcohol, lye, acid, various high test solvents, etc) will damage the lungs in rough proportion to the type and amount of the disinfectant used. The virus is, for the most part, not just lying around on the interior surfaces of the lung. For the chemicals to kill the virus causing the damage they would first have to penetrate the various lung structures and cell walls, damaging the structures and killing the cells in the process. In addition, the lung damage caused by these chemicals is the type of damage that can result in ARDS, which is similar to/the same as what is often the end stage killer in COVID-19.
There are some ionized gases that will kill nearly all bacteria and viruses present in the area of effect. Such a gas (ozone for example) could easily be introduced into the lungs in a controlled manner. The problem with using such gases for treating pneumonia or other pathogenic lung diseases is that they have been shown to trigger cell death (apoptosis) and/or cause tumors.
As for UV light, unless the COVID-19 virus takes up residence on or a short distance under the skin, the UV wavelength that can penetrate any distance into the human body will not have any direct effect.
A process called Ultraviolet Blood Irradiation (UBI) was tried in the late-1800s/early-1900s, and one study reported a 100% success rate (75 out of 75) vs pneumonia. If this success rate were true, any responsible physician should be using the UBI process in place of pretty much all other treatments (today's fatality rate for pneumonia being treated in a hospital setting with antibiotics/antivirals is 5%-30% depending on the type, with an overall average of 5%-10%). UBI is apparently not used at all?
To use UV light internally is physically possible, and has been tried on otherwise probably terminal pneumonia patients. Once again however, the virus is for the most part not just lying around on the interior surfaces of the lung. An relatively powerful light source would have to be used for the virus to be killed in "a minute" or so, powerful enough to penetrate the mucous and other fluids (ie saline, blood sera, etc) coating the lung structures, the lung structures themselves, cell linings, etc. That much UV will itself will cause damage. A less powerful light source could be used for a longer time, but since the effects of such radiation is cumulative, the damage would still occur. As I said above, the process has been tried, using nasal/trachea passage of leads, but the success rate was apparently nil. If it had looked promising, the method would be in common use for the more serious pneumonia cases at the very least. It is apparently not used at all?