I haven't done any serious distance hiking, but from my indirect exposure to Canadian trails through the media or happening to be vacationing in the vicinity, or short forays, or on a mixed use trail where I have sometimes biked a segment, I am sure most have minimal en route facilities except at nodal points like a town or a vacation site that serves as a trail head/access point. Still, I assume that some of these stopping points have laundry facilities that are available to hikers either in a public campground or in private businesses. Presumably people who are doing a 2000 mile trek have to have clean clothes from time to time.

In Ontario we have the 500+ mile Bruce Trail that follows the Niagara Escarpment which cuts across southern Ontario and my daughter has done a lot of day hikes on it. Part of it goes through farmland and part through short stretches of wilderness but you're never far from a town, so if you were hiking it as part of a multi-day trek you could easily find a laundromat and grocery store for fresh produce every couple of days without going much out of your way. I presume farther north there are some much more remote trails, but it's not as big a deal here as the Appalachian and Pacific Crest Trails, partly because there are so many rivers and lakes to cross. Thus, we have more of a tradition of modern adventurers following remote historic canoe routes, but apparently that is somewhat dying out, and I hear canoe outfitters and guides and so on in places like Quetico (northwest of Duluth MN) and the corresponding Boundary Waters (US side of same area) are struggling with declining business. Canoeists can of course carry a bit more than hikers, so they should be okay for many days or even a couple of weeks without support. And there is lots of water!

I don't know much about hiking elsewhere in Canada. In theory we have the TransCanada trail but it's 90% fiction.