I love them, but my kids are brats!!!!?

I have three year old twins. They are cute, funny and smart, but also smart @$$es. They tell me no, they call names, they run away when they are in trouble, they kick when they get punished, they yell and scream at me when I punish them, they throw toys, and the whole nine yards. I have done everything. I have tried positive redirection, time out, the chair, go to bed, , take toys away everything. I dont punish with food, like "go to bed with no dinner" but I wont allow sweets if they misbehave. I yell, but only to get thier attention, and rarely at them, just like HEY LISTEN and then I speak.. every time I try something new, i am very consistent, try it time and time again.I always praise them when they do something good, use manners or do what I asked of them. I also try to understand, there is two of them one of me. and they are three. But sometimes I have to them, often. When I do I am not gentle, and I dont take it easy on them. They laugh it off. wht to do?