A16-fl oz bottle cost 2.00$ what is the unit cost

Unit cost is per unit, could be per oz, or per bottle.
Since unit cost per bottle is already given, we assume unit cost required is per oz.

16oz costs $2.00
1 oz costs $X.

Cross multiply,
16X=1*2.00
X=2.00/16 = 0.125
The unit cost (of capacity of bottle) is $0.125 per oz of bottle capacity.
or
The unit cost of the bottle is $2 per bottle (as given in question).