Sure, I just made some last week. Find a brand that does not contain milk/eggs in the muffin mix (many brands of cakes, muffins, etc. do not). Then add diet or regular lemon-lime soda until it had the right consistency for muffins (nearly a whole can for me). Bake them like regular muffins. Works great.
Also, if you want glaze but the glaze contains milk (which it often does), make your own with an online vegan recipe for lemon glaze. There are a bunch and since its vegan it won't have eggs or milk or anything.
I do cupcakes/muffins from boxes like this all the time because I have vegan friends (and frankly it's easier and cleaner). Even my non-vegan friend like them a lot.
Hope that helps.
Medium Goal #1 - Done!
Medium Goal #2: