The Japanese tanka is a 31-syllable poem, often written in a 5-line, 5/7/5/7/7 syllable count form.
The tankard extends this form slightly:
5/7/5/7/8 = tanka + one for the r(oa)d = tankard
A tankard is best written in the company of a pint of beer.
Here is the eponymous (and autological) poem from Kneptune, where the form originated:
TANKARD
picking a first draught
you settle on an order
get comfortable
pencil and paper ready
then artfully raise your tankard.