I'm writing a book, but I can't think of a title for this book. It's kind of like The Hunger Games. It's set in the future and there's just one small city left behind after the destruction of Earth. A group of 5 friends decide to go against the laws of the city and they venture out, hoping to find adventure and answers to past life. The book will have some romance, betrayal, friendship, mystery, and adventure. Please help me come up with a book title idea for this, Thanks!

A lot of times writers will use a 'working title,' something that was easy to think of but isn't what they want to end with.
You have done quite a bit of plot development all on your own, so eventually the title will reveal itself to you without help!
I loved Hunger Games, BTW. I guess a lot of us did. So much better than the movies of my younger years on the subject, like Logan's Run. Maybe I shouldn't be so hard on that old movie. I hear they are going to remake it. It's worth checking out.
I might just pick a joke title for now, ending in games. Starving Games, End of Games, Coffee vs Tea Games, Real Games, Unreal Games... I like End of Games for me!

There very likely will be a phrase that grabs you as you add it to the narrative or dialogue, and that phrase will make sense as the title. Meanwhile, like joy suggests, give the book a working title.