Preheat your sandwich maker according to manufacturer's instructions.
Spread mayonnaise over 2 slices of bread. Cover with marmalade. Spread potato chips over marmalade. Lay pineapple over chips.
Break apart sardines in a bowl using a fork. Spread on top of the pineapple slices. Season with salt and pepper; cover with the remaining 2 slices of bread.
Toast in the preheated sandwich maker until brown and crispy, about 5 minutes.
