First, choose the scents you want to use in your bottles. I chose almond, orange, cinnamon, lemon, peppermint, and vanilla (not pictured) extracts. A good variety of strong scents will be your best bet for being able to sniff them out once they are in the bottles.
Next, take a small cotton ball and soak it with the extract. Then shove the cotton ball into a small bottle or jar. I used travel sized shampoo bottles. They are inexpensive and they have the added bonus of a screw-on top that then pops open. No fear of the kiddos dumping extract all over the place! I also added just a few extra drops of extract directly into the jar. The cotton ball quickly soaks it up and it adds just a little extra punch of smell.
Finally, screw on the top and let the kiddos go to town! This is actually a really fun game for kids of any age, including adults. My husband and some colleagues at work had a blast trying to guess what they were smelling. (I helped myself by putting a clue on the bottom of each bottle in Sharpie.)
For someone of L's age and experience, this was more of a getting-to-know-new-smells kind of activity, but with older kids it's fun to encourage them to try to identify what exactly it is they are smelling.
L didn't really know what she was smelling, but that didn't stop her from trying out each of the bottles!
She even decided to give a few other things a sniff, including her dot markers! Gotta love that sense of curiosity!