Is It Okay To Eat A Little Unhealthy?

I've been working out and eating usually eggs with fresh veggies, fruit, and oatmeal for breakfast, lunch a couple of porkchops with sweet potatoes and in between snack on lightly salted cashews and beef jerky. Late at night I get hungry though and have old cravings. I'm 5'10 and weigh 215, I'm not trying to lose weight per se, I'm really just trying to get built and and look good without a shirt on. Turn it all into muscle. So is it okay for me to cheat a little like at night eat something microwavable and have a frappuccino or should I not? Just let me know please also like I said I like my size I don't look fat besides the guy I'm starting to get. People ask me a lot if I work out and I really don't (just started again a few days ago) so I actually like this weight, I'm a pretty big stocky guy and I feel like I have the right body type to get big and buff, so what kind of diet should I have, what kind of exercises should I do to just turn this flab into muscle and look damn good without a shirt on while maintaining the size I'm at now.