Your dog knows what you want when you ask him to "give sugars" or "gimme kisses." It's a very human way of expressing love to the dog. He understands what you want, but does he understand what smooches actually mean? He doesn't really know at first, but he can come to learn it's a gesture of affection.
Do Dogs Know What Kisses Are?
Dogs have no innate understanding of kisses
Humans and dogs have different means of communicating. Overt human use of body language is generally limited to broad and easily read gestures; however, dogs must rely on what we'd see as subtle gestures and expressions as well as broad motions to make their thoughts known to each other. The language they "speak" does not include kisses in the sense humans know them. They do share gestures of affection, such as touching or rubbing against each other or licking each other in a social way. Meanwhile, most dogs are good at figuring out our communications to them, a trait they have developed over millennia of domestication.
How dogs “kiss” each other
It's true that licking and nose bumping are part of dogs' repertoire of affectionate gestures. One of the first experiences in a puppy's life is being licked by its mother immediately after birth. Dogs lick to express affection, to show submission, and to gather information. When a dog licks itself or another dog, it releases endorphins — stress-relieving hormones — making it a pleasant experience. These gestures are not kisses as we understand them (that is, they are not primarily performed to express love and affection), but they can serve many utilitarian functions as well.
Teaching a dog to "kiss" you
Dogs learn our body language and our vocal inflections fairly rapidly, especially if we are clear and consistent in communicating with them. Most are interested in your attention enough that any encouragement will cause them to come nuzzle any part of you that you make available, be it your cheek or your hand or your lips. It is possible to train a dog to "kiss" you, with a nose bump or a lick or a nuzzle, by holding a treat — in your hand for hand-kissing or next to your face for cheek-kissing — and encouraging him to lick it. You may consider smearing a touch of peanut butter on your cheek to get him to lick you. As soon as your dog understands what you expect of him, add the command, such as "sugars" or "kisses" as you would training any action.
Kissing dogs and safety
Not all dogs enjoy having their faces near human faces. If your dog feels threatened by a human face up close, do not force him to learn to kiss you. A dog who's not into it will give you warning signs such as turning or growling. Do not put him in the position of feeling forced to protect himself from you and biting you. Children, in particular, should be made aware of the risks of putting their faces near dogs' faces and should be taught the warning signals.