If a condiment counts as an ingredient:
Leftover rice, chili paste, fried egg.
Leftover rice, kimchi, fried egg.
Kimchi butter noodles (fry kimchi in butter, add cooked noodles)
Leftover spaghetti fried in chili paste.
Shredded cabbage tossed with mayonnaise and Sriracha
If bread counts as an ingredient
Avocado toast with chopped onions.
Avocado toast with fancy cheese
Cheese and crackers with olives.
A margarita - 2 parts tequila, one part orange liqueur, one part lime, shaken with ice. Plenty of 3 ingredient cocktails!