The first step is to realize you did NOT gain body fat.
Just because you step on a scale and it shows a higher number, does not mean you gained that much fat.
Naturally, if you ate more food, you'll weigh more.
The human body does NOT put on body fat that quickly, except for in extreme circumstances.
If you wait several days after you return, let everything "pass through," and you'll see your weight return to baseline.
But if you're someone watching what you eat and (hopefully) tracking calories, then you should make a decision as to whether it's worth continuing to track on your trip.
If you decide you want to enjoy your trip without tracking, and that's fine - just make a point to consume 10-15% less food/drinks than you normally would.
Notice we're saying 10-15%... not 25% or 50%. Keep the reduction very moderate and just enjoy yourself.
Extreme measures never work.
Come back, get back on track, and watch how nothing changed, because vacation weight gain is not real weight!
If you are serious when you return home to lose more weight you should consider taking a look at our various programs. We are determined to help people like you and ourselves lose weight and keep it off!