I was thinking more along the lines of

Upside: Speed increased by 60% when consumed, for 8 seconds

Downside: For five seconds after effect ends, speed is decreased by 60% of base
Although your description is nice, I'd like a speed boost effect more than crits, gets me to the frontlines faster. I like the item though.

No No No i think its more like

+ Reduces all damage taken 95 for 8 seconds.

- lose 30 health after effect ends (due to human anatomy, beer can destroy your liver)

+30% healt for 60 seconds

+30% speed for 8 seconds when consumed.
Applies jarate effect for 8 seconds on you when consumed.
Description: I like this! Wait. Why does this smell like Jarate?! SNIPER!!!

No random crits, now its balanced!

Effect
Primary Weapon Minicrits for 10 seconds, but 5% Less Accurate

So your original stats make it a DIRECT upgrade to the Kritzkrieg's uber, which gives 8 seconds of kritz, at the cost of a measly 96 damage to self? WAT? I like the idea of full kritz from a lunchbox but SHEESH.

OK guys, in here to save the day with my un-professional stat ideas that are suitable and balanced for the game. (Maybe).
When activated:
+35% movement speed
+25% more accuracy
+ 50 health regained
+ 8% damage resistance
- 1.5 extra second of drink/eat time
- when activated -30% max overheal
Lasts maybe 6-8 seconds

jjdefender did a nice job with stat ideas, but if you ask me, it needs a little work as there is barely any downside.

now because this is an alcoholic beverage, i like the idea proposed by Dan Hibiki that after the effect ends there is a negative side effect. perhaps a weaker and opposite effect on the player.

so if it gives a +35% move speed the after effect would be a -17% movement speed
the +25% accuracy would translate to -13% accuracy
since it is a lunch box, draining the 50 health it provides would probably break the weapon.
the +8 percent damage resistance would turn into a -4% damage resistance

personally i think all lunchboxes should have the same consumption time
the -30% overheal is nice
and the effect should last 8 seconds with a 4 second drunkenness afterwards.

if anyone has any thoughts on this or would like to add or change this. please feel free to write

+25% damage resistance from all sources when consumed for 30 seconds
marks you for death for 15 seconds after effect has worn off (bubbles gives heavy a headache)

or alternatively

+25% damage resistance from all sources when consumed for 30 seconds
-20 less accurate for 15 seconds after effect has worn off (again, the effects of the headache)

EDIT: or maybe both?

I like the various temporary speed boost ideas, as Heavy needs something to get him to the front lines faster. If this is followed by a brief speed debuff once the boost wears off, then I could live with that.

I would like it as a taunt but not a weapon.

+ 50 health regained
+100 afterburn
- you will in to pyroland for 30 second because this item to many alcohol

Here's my idea:

+ Upon drinking, Heavy gains a 50% speed boost for 8 seconds.

+ Gives heavy 100 health. Animation takes one second to complete and add buffs

- Cannot be thrown

- Upon drinking, Heavy takes 35% more damage for 8 seconds.