Fill up with gas before you cross the Canadian border.
Cola will be available, but cheaper in the lower 48. If you have the space, stock up (for the cost savings). Another thought on soda...if you plan on driving a lot of the dirt roads (such as the Denali Highway), and if your rig rides rather rough over potholes and washboard...go with anything but cans. Modern aluminum cans are so thin that they don't travel well with all the motion, and are prone to leakage. Plastic bottles are best, and even glass is preferable to cans.
Food will be available, but cost more in Canada and as you head north away from the major population centers. So, you would do best to stock up on staples before leaving, and then only have to pick up perishables along the route. Heading home, stock up in Anchorage or Fairbanks.
That said, be sure to check out the local groceries and try the local fare. As previously discussed, Canada has an amazing variety of potato chip flavors that we don't see in the US.