How old does your child have to be before you can give them sweets like cake or chocolate? :)

Try not to introduce sweets before they turn one if you don't want them to be picky eaters. Our pedia said not to introduce sweets, salt and other artificial flavors to our toddler's food so that he doesn't grow inclined to those food only. I use herbs to add flavor instead and switch things around every now and then just so he doesn't get bored with his food. There are a lot of healthy recipes which you can easily whip up from the internet :)

As far as I know, 1 year old can now eat a little bit more of sugar. That's way if you'll notice, they have the cake smash tradition where they let the baby mush and eat the cake.

My bad. My baby tasted (more of lick) sweets at 7months. But if we're talking about eating ice cream/cake/chocolates, I'm planning to introduce it once she turned 2 years old.

A year old would be fine. I even encourage the baby to try all types of food so he would not be picky.