Answer:
I am the kind of soda you must not drink. What am I?
As a state in America I am round on both sides and high in the middle.
Take it and you will lose or gain more than the others.
By myself, I'm practically nothing. Worthless as a leader, but when I follow a group, their strength increases tenfold. What am I?
No matter how hard you hit me, no matter how much I hurt, I'll always go for a laugh. What am I?
Sometimes I am white, sometimes I am dark. Most people love me. What am I?