I made some homemade ginger beer using a ginger bug and bottled in a glass flip top bottle. I brought a bottle to a friend we drank half and it has now been in the fridge sealed for a month and a half. I know that refrigeration slows down but doesn’t stop fermentation. Do i need to be concerned about it exploding if/when i try to open it now? Are there safe ways to slowly release the gas? I’ve made this recipe a bunch of times and never had a problem, just feeling unsure about the length of time sealed in the fridge.
There are two ways a bottle can explode, fast and slow.
Fast happens when there is still too much sugar in the solution and carbonation is still going on. This will mostly happen fast, surely within a week or two. The pressure must become really big for that, though. This would be an amount of sugar greater than 9g/l (to be sure, some bottles can withstand more).
Slow happens when the pressure is correct, but the bottle might contain a mechanical failure. I had this with a saison beer. One bottle was neatly separated from its bottom.
Bottom line: I don't think you have anything to fear. Opening the bottle will not make it explode, on the contrary. Opening the bottle will always immediately release the pressure. And if you want to make sure, wrap your bottle in a towel when handling it for opening.
Update: since you confirmed that the bottles are beer flip-top bottles, you can be sure that they can withstand a whole lot of pressure.