Second, what would they be testing? Drugs for their condition? That wouldn't apply to the type of situation necessary for euthanasia under Canadian law[2]:
>To be considered as having a grievous and irremediable medical condition, you must meet all of the following criteria. You must:
1. have a serious illness, disease or disability
2. be in an advanced state of decline that cannot be reversed
3. experience unbearable physical or mental suffering from your illness, disease, disability or state of decline that cannot be relieved under conditions that you consider acceptable
If there was an experimental treatment that might actually help them, these criteria would not apply.
If you're suggesting safety testing of drugs for other illnesses, that's extremely unethical and I seriously doubt the medical community would be willing to do it, even with consent. And I seriously doubt a number of people large enough to give meaningful results would consent in the first place. It's also of dubious usefulness because any treatment intended for disease X might have its safety profile and risk/benefit analysis altered by the presence or non-presence of X.
1: https://www.canada.ca/en/health-canada/services/health-servi...
2: https://www.canada.ca/en/health-canada/services/health-servi...
Although it does seem like many companies are still not allowing this. I don't know much on the topic and I'm not sure why (financial reasons perhaps?) they'd refuse, but I've always found it absurd that we can poison ourselves to death (literally) with all sorts of substances legally, but experimentation with life saving methods are restricted. I've seen some very strange arguments against the experimentation like "well they could die sooner!" - yeah, but that's up to the person to decide, just like all other decisions they've made preceding it. A patient has the right not to choose any treatment at all, that could definitely make the die sooner. Why is this where the line is drawn for some people? It seems arbitrary.
Unfortunately, using it in a non-study context risks a whole lot of confusion-- if the marginal, near-death case that wouldn't qualify for your trial dies in a weird way, what do you do?
Not to mention that prior to approval, there are no economies of scale in production.