Skinny people eat junk sometimes. Moderation really is the key.
Yesterday I had:
600mL bottle of solo with lunch at work
Hungry jacks kids meal (small chips, hamburger & diet coke) for dinner with the boy (really good option actually, kept me full for hours)
1/2 a pack of dark chocolate maltesers at the cinema (the boy had the rest of the pack plus a pack of m&ms haha boys)
I don't know, if I were still counting calories I'd be beating myself up about eating that because it's huge. But I really enjoyed it, probably more so now I've been on a few diets.