if you don't have refrigerator space...
for protein: salami, jerky, canned fish (I prefer canned sardine, and salmon, they are less dry than canned tuna straight up)
whole food snacks that doesn't need to be refrigerated: nuts+ seeds, avocado, tomatoes, fruits, nut butter
other: tetra-pak milk/ chicken broth/ other beverages. single pack miso soup paste (just add hot water, you can take some dried seaweed/ mushrooms with you too)
Usually on the first day I arrive, I go to the grocery store.
The posted links are great, I am learning a lot of tricks here...