Rapid increases in weight over a night is usually caused by water retention. Various things can cause the body to hold more water for longer, so the overall body weight goes up. The effect can last a few hours to a couple days depending on the cause.
The most common culprit is salt because restaurants love putting salt on everything. It also makes you thirsty so you drink more. Starchy carbs like potatoes will also cause water retention.
A secondary cause is you may be underestimating the portion size of the meal. Eyeballing portions is a learned skill which is why some people will actually bring mini scales. Restaurants sometimes also add oils that go unaccounted for.