Peelable fruits are easiest (i.e. oranges, bananas).
Candy, chips, etc. with a hechsher are easy.
Most canned tuna fish has a hechsher and mayo with a hechsher is easy to find. Tuna salad can easily be made with only disposable utensils.
If you are looking at bagels and cream cheese you may want to get lox which is readily available with a hechsher in many non-Kosher supermarkets.
Hummus (such as Sabra brand), guacamole, peanut butter and jelly are also widely available with a hechsher.
Many bottled drinks have a hechsher: water, orange juice, apple juice, soda, etc.
If you can get (and toivel) a new electric pot that can boil water, then foods like hard boiled eggs, egg salad or macaroni and cheese become possible.