DS is 28 months, and gets a mixture of treats. DH and I tend to not eat anything ourselves that we wouldn't with him (exception being drinks - fizzy drinks, caffeine and alcohol of course!). Which makes us eat more healthily - we don't buy junk on the whole, but living overseas don't have access to the Organix healthy-snacks-for-kids ranges so have to be a bit more creative.
So, DS gets.... diluted apple juice about 3 times a day while it's so hot (demanding it over water right now); mini smarties in a little box for long car journeys (those over 2 hours, which we do a couple of times a month), and when we potty trained he had a smartie for wees and poos for the first few days - we phased this out to just verbal praise without any problems.
He has ice-cream or an ice lolly (either bought while we're out, or in a bowl at home) about 3 times a week. We don't buy biscuits, so just breadsticks, crackerbread or rice cakes. But if he saw them at someone else's house I'd have no problem with him eating them. Every other Sunday we'll buy pain au chocolate or croissant and he'll have one to himself. He has a fruit-flavoured Petite Filou every other day. We have chips, either home-made wedges or frozen oven chips, once a week - usually on Friday night with pizza.
When we fly (about every 2-3 months) we load up on pombear crisps (or Organix if we can get hold of them), chocolate raisins and chocolate milk and other baddies proportionately to the length of the flight. (i.e. a 1 hour flight we'd just give him milk in a little carton - 8 hours would be quite a bit of chocolate and crisps).
He eats about 3 pieces of fruit and day and tons of veg (we grow some, including cherry tomatoes in pots, and he grazes on them whenever in the garden). He won't eat much meat or fish, unless it's breaded, in nugget form and dipped in ketchup, but is great on vegetables and loves broccoli, spinach and the rest. So you win some, you lose some!