The egg tends to land in your hands.
Work Step by Step
When the car is traveling at a constant speed, everything in it is traveling at that speed too. So both you and the egg are traveling at that speed. When you toss the egg in the air, it doesn't lose any velocity because there are no forces acting upon it besides gravity. So, the egg will travel the same distance as you in the air, then come back down in your hands where it was before.