True wassail song (as in, sung at Christmas time) - how about any high-voiced
transposition of any decent wassail song? The downside being that most wassail
songs aren't interesting unless they're sung in ensemble with harmony -

If what you really want is a DRINKING song expressly written for soprano, you're
probably somewhat out of luck. You could transpose upwards the Brindisi (Il
segreto per esser felice) for Maffio Orsini in Donizetti's LUCREZIA BORGIA -
- or sing Turridu's brindisi
("Viva al vino!" from CAVALLERIA an octave up -
- or sing both Violetta's and
Alfredo's parts of "Libiamo" from TRAVIATA (his an octave up) -
. Or you might get away with
the delightful "Ah! Quel diner!" (more of a "Drunken Song" than a "Drinking
Song") from LA PERICHOLE.

Some other operatic brindisis:

Enrico's [tenor] ("Mesci, mesci) in Donizetti's IL CAMPANELLO -

Pippo's [contralto] in Rossini's LA GAZZA LADRA -

One of my favourite all-time drinking songs is by early baroque composer Adam
Krieger, "Der Rhein'sche Wein", which I'll be performing in a concert of his songs
in December - (easier to make
out the lyrics here - but the tempo is too slow IMO -

Another is the wonderful drinking song from Carl Orff's CARMINA BURANA, "In
taberna quando sumus" - - (and
another setting more contemporary with the text -
- and a solo version -