General terms:
* Miniature
* Vial
* Phial
* Ampoule
* Dropper bottle
* Sample bottle
* Tiny bottle (sometimes used playfully)
More specific terms:
* Scent vial (for perfume)
* Essential oil bottle
* Medication bottle
* Eyedropper bottle
* Test tube (if very small and cylindrical)
* Flask (if very small and round)
The best word will depend on what the bottle is used for and what you want to emphasize.