It’s not realistic to brush your teeth immediately before kissing someone. If you’re really hoping to create a perfect kiss later on, just be mindful of foods that aren’t going to fade off your breath right away (like garlic or tuna) and avoid those.
Mints and gum are also a quick fix that you can pop in if you sense kissing might be in your near future. When the time comes, your mind will be at ease. If you’re not feeling self-conscious, that’s going to make the kiss that much better.