Drinking and those pve skills

To get bonus on skills such as Drunken Master, do I need to be drunk as in lvl3 or it's enough I drink one Eggnog or Dwarven Ale for instance?

one dwarven ale or egg nog always seems to work for me.

drunk as in level three i believe, so a level 5 drink will do the trick

lvl 1 drunkness has worked for me, but if you are working on the title, might as well use a lvl 5 drink.

lvl 1, hands down will work. The skill says you have to be drunk. Level 1 is a certain point of being drunk, though it is the lowest. Level 3 only counts as intoxication and that is just a different term for drunk at that level. You're good with drinking just one to get the effects going. I would suggest though to bring it up maybe by 2, or even three. If you're working on drunk title just get the 5 level drinks, like the guys above me said. You can find out more in the wiki for successful drunk title acquiring.

[[Drunken Master] only requires one level of drunkenness to get the full effect.