Well thanks @BlackHaddock for another Stat Attack, however this is the only time you will see Jersey & Guernsey together in any entity, as there is a very strong rivalry between the 2 islands!
There are 7 Channel Islands of any decent size in the French ‘Bay of Saint Malo’, The ‘Bailiwick of Jersey’ (45 sq miles of main island + off shore reefs, some with seasonal fishman huts)
The ‘Bailiwick of Guernsey’ (25 sq miles of main island) also consists of the smaller Channel Islands of Alderney (5sq miles), Sark (3sq miles) & Herm (1 1/2 sq miles) plus the privately owned Jethou & Breqhou islands.
Beer wise - Jersey has 3 breweries, Liberation Brewery celebrating it’s 150 anniversary this year, and the fairly recently formed Stinky Bay & Bliss. The 3 breweries are working together for a much awaited Christmas collaboration!
Guernsey also has a long established brewery, Randalls, plus it did have a smaller brewery called White Rock which sadly closed last year. There is a newly established microbrewery called Little Big Brew Co.
As @LazyPyro stated Sark does (or did) have a small micro brewery
Jersey beers top 3 - Bliss Intergalactose & Bliss Cream both with 4.0 ratings, Liberation 145 Double IPA with 3.8 rating
I really can’t comment much on Guernsey beers (or places for that matter) as while I’ve been 5 times I’ve not been there (unless enroute to Sark or Herm) since 2010.
Funny enough knowing I’m overdue a visit, I just looked last night to take the very short flight (10 min) to Guernsey, prices are 1/3rd more expensive than for me to fly to London (1hr)!!
What Guernsey beers I’ve had was from that 2010 trip or the odd bottle / pint in a Jersey supermarket / pub since then. I nearly got my hands on the Sark beers, my wife was going to the brewery for me on a visit to the island in 2019, but then alas the ferry was cancelled for bad weather.
Jersey places - 1 stand out for me - JB’s Brewhouse which is where Bliss Brewery are based, besides the great Bliss beers they have a strong line up on tap & can. They also do immense smoked meat if your into that.
The other place really worthy of visiting regular for me is Krafty J’s, a small crafty micro pub on a town square with DJ tunes in the evening.
Jersey’s got plenty of traditional pubs, some such as the Lamplighter & Prince of Wales Tavern in St Helier with half decent UK Cask ales, a number of the islands pubs are owned by Liberation Brewery which will have a decent range of there beers, then there are almost a equal number of Randall’s (Guernsey based) pubs, (which I try to avoid) with if your lucky 1 UK mainstream cask ale (never for some reason having the Randall’s beers brewed in Guernsey).