If you don't want to use treats or simply want to do something different, get a friend or family member your dog is interested in and have them go hide while you keep your dog distracted. Once they've hidden, let them go and give them the command "find _____" and let them use their noses to seek out the hider. The best part is they can have praise and pets once they find who they're looking for!
Like the cup game, Which Hand? is another quick and easy game you can play to get your dog introduced to scent-based games. All you have to do is hide a treat in one hand and hold both out for them to sniff and choose. The best part is, once you play a few times, both hands will have scents in them, which will naturally increase the overall difficulty.
When your dog can't see (or isn't looking) place three non-transparent cups on the floor upside-down with a treat under only one of them. Invite them to come over and see if they can identify which cup is hiding the treat. When they find it, lift it up and let them enjoy!