The best places to cache food are Longmier, Mowich Lake and Sunrise. You will use 2 out of the three depending on where you start.
My preferred start point is Mowich Lake, but I have started at other locations. Places where you can safely leave a vehicle near the Wonderland Trail are Longmier, Mowich Lake, Sunrise, White River, Fryingpan Creek, Box Canyon, Reflection Lakes, Nardia Falls, & Cougar Rock.