Anne-marie,
you didn't mention whether he was having chemo or not - that could definitely cause nausea issues. Without chemo though, it seems a little early for radiation sickness. Many of us were sick a lot, especially towards the end and post Tx. It comes with the territory. I honestly can't imagine that chocolate milk and gatorade would combine well. The mucositus can cause nausea but without chemo that won't be as severe. You can easily have nausea just from anxiety alone. The Vicodin may play a role as well. I would avoid anything acidic at this point. Ask the doctor about antiacids.