I'm not a doctor but IME, Vyvanse doesn't make you ill if you drink. It's not a good idea to drink, as you have to stay hydrated and alcohol dehydrates you. Mainly IME, I never felt intoxicated from alcohol while on Vyvanse. It's not like Antabuse, for example.
Stick with your prescribed dosage. The initial, mild euphoria is short-lived, but you will feel that nice pick me up when you take it. Takes a good hour or two to kick in.
You can really focus and get stuff done but it does NOT motivate you. That is where you decide you're going to get caught up with a school or work projects, etc. you can easily blow hours on the internet (porn is common and increased smoking).
So if you're not using it recreationally, keep track of your time. Get up and get going on that task that needs done. That is you motivating yourself and Vyvanse will keep you focused and efficient.
Stay hydrated and eat something every couple of hours. A yogurt and a banana. Some protein. Even a spoonful of peanut butter. Drink water. Lots.
I no longer take Vyvanse as it was too expensive for me and only lasted 6-8 hours, not 12. Just swallow the pill. No other ROA.
Hope this helps. It shouldn't make you crave alcohol but I don't know why your doctor thinks otherwise. Maybe I'm wrong. Just don't redose. You gotta get sleep. Food, a shower and a benzo (I'm prescribed Klonopin) is good for the comedown, which is more minimal on Vyvanse for most. Benzos probably not good for you. It's not critical to have....basically you can mentally learn to chill without a drug when vyvanse is wearing off but you're not sleeping yet. Some people like a darkened room, headphones with good music, Netflix, sex, etc.
Hope this isn't against the rules....ADDforums dot com is a good resource. There is a subforum for Vyvanse and also one for addiction. One of the mods is a recovered alcoholic. I know your main focus is sobriety---you can keep it up!
I have a rule where if I run out early, tough. I never buy off the street and I'll never try meth. I learned my lesson on redosing and follow my rx instructions. Don't chase the dragon, he's gone. But it's still working, it's just subtle. Tolerance takes quite awhile to develop of taken as directed, IMO.
Take care.