This same sort of thing happens with lots of brands. Drinks, food, apparel, whatever. My friend's band was sponsored by Red Bull and just got shipped cases of it wherever they were on tour. No obligations to promote Red Bull and the most that probably happened was they were put on a list of bands that Red Bull sponsored.
Free food is HUUUUGE when you're on tour, doesn't matter if it's Taco Bell or whatever. If you're broke and can barely make gas money you will eat free Taco Bell even if it means suffering the afterstench in a van with 7 dudes (had to deal with Taco Bell consequences even though we had to pay for it).
Does anyone actually think being sponsored is selling out? Come on now, we all love free shit.