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!