For me on trips, I either take food with me (road trip) or utilize grocery stores. It is pretty easy to pick up stuff in a grocery store and many hotels these days have fridges but I always request one if not. I also carry things with me that are portable like Luna bars. Also plain oatmeal packets are very portable as are raisins and a packet of cinnamon or even making your own.
This last trip, we went to Disneyworld and chose a hotel with a small kitchenette. We headed to the grocery store, bought a box of cereal, soy milk, blueberries and bananas. It worked out well for breakfast.
Of course those are my choices and it works for me.
You can't out-exercise poor eating habits.