TODAY YOU FINISH BRUSH-TEETH YOU? (Did you brush your teeth today?)
* This particular use of this particular version of FINISH means "have you," "did you," or "already."
(The sign FINISH has many different versions depending on how you do the sign.
The sign FINISH can be located before the verb to create what is called "perfect tense."
See section 5: "Preverbal FINISH as a perfect marker in ASL"
of this research article:
So, "TODAY YOU FINISH BRUSH-TEETH YOU?" means "Did you brush your teeth today?" and/or "Have you already brushed your teeth today?"