Sack and Canary are alcoholic drinks referred to several times in 17th century broadside ballads.

The earliest text I know of for "Will you go to Flanders, my Molly O" is that in Herd's Scots Songs, 1776, as I noted in the third note above. (which also notes where you can see that text)

I would be very interested to know if there's real evidence for the song being of 1706, or it that's just an 'educated guess'. King William was fighting in Flanders as early as 1692. Several 17th century broadside ballads on this subject can be found in the broadside ballad index on my website.