Riddle poem 2

A riddle in a poem, can you find the answer?

I come in all sorts of colors

And go from oval to round shapes

Though not big, flat or abnormally thick

I serve multiple purposes

But all come down to one

I can be bitter, sweet or non flavored

Though most of the time

You won’t taste me

You use me more often then you might know

Find me in the bathroom

Or in your night locker

Maybe even in your purse

Liquid is my best friend

But sometimes all I need is saliva