Re-Carbing commercial brew in rented keg

Got a quarter barrel for new years for myself and a couple buddies. We didnt end up getting through all of the beer and now its sitting in my garage. I re-tapped it last night but its pretty flat beer. We were just using a party tapper from the liquor store.

Is there anything simple I can buy that will allow me to re-carb this keg? maybe something that uses those little paintball canisters?

I dont have any kegging setup to speak of and I'm mostly unfamiliar with the names for things, but I know that this keg I have has the same fitting as my keggle did before I cut it up. Sanke connection I think?

Any suggestions appreciated. Thanks alot!

It's possible, but there are a lot of issues with your plan. The first one is that using the party pump has oxygenated the beer, and by now it probably has a noticeable wet cardboard flavor, which will only get worse over the time it takes to carbonate. You'll also need either a standard sankey keg coupler (like you'd use with a CO2 tank) or to destroy your party pump coupler. A portable keg charger like this one will then work with the proper fittings, but will require a lot of cartridges to carbonate and serve the remaining beer.

if you used one of the party taps the life of the beer is limited. It will start getting that wonderful cardboardy oxidized flavor to it. I would suggest drinking it quick. You can kind of recarb it by putting it on CO2 but it is still a ticking clock.

I have one of those portable beer chargers and they WILL NOT carb beer. They produce enough pressure to push beer, but it would literally take about 15 of the small CO2 canisters to add any appreciable CO2 to a 5 gallon corny, let alone a 15.5 gallon keg.

You would need AT LEAST a 20oz CO2 canister to carb 5 gallons of beer, and that would cost about $25 for the canister, another $15-20 for the regulator, a couple bucks for tubing, about $8-10 for the CO2....all of which definitely equals a pretty poor ROI just to carbonate some old, oxidized beer.

I own all of this type of equipment, and I wouldn't even waste my CO2 trying to revive this beer.

Uncarbed beer isn't horrible if you get it cold enough. Lots of Europeans even prefer their beers served uncarbed or very lightly carbed, furkin/cask conditioned style.

I think in the end, you just need to let it go

Drink a 12 pack of carb'd beer first then you won't know the difference.