If you find that your cold beer is a little acidic, it probably hasn't been extracted enough and you just need to prepare more. Add an hour or two or use a finer grind setting next time if you use the immersion method. For the slow drip method, use a slightly finer grind. Sour coffee is usually the result of a short preparation time, which means that the sweet flavors are not fully extracted from the bean.
Increasing the preparation time will allow all the tasty flavor compounds to be extracted from the drink. If your beer is too watery right now and changing the proportion or brewing time doesn't solve the problem, grains could be the problem. Making a concentrate allows you to drink a good cold coffee drink without sacrificing flavor as the ice melts. You can follow a tasty recipe, use the best filtered water and let it sit for the right amount of time and still get a bad tasting cold infusion because you opted for pre-ground coffee.
Lighter roasts can be a little difficult to do well and, especially with cold beer, you don't have much control to do it right every time. This produces sour or bitter cold beer flavors, which is the last thing you'll want to drink in the morning. When the taste of cold beer is missing in action, this indicates that there is a problem with the quality of the water or coffee beans. The oils and solids left over from the brewing process can add sour and rancid aromas and flavors to coffee, even if the beans are freshly roasted and ground moments before preparation.
Of course, you can also go the other way and make sure that there's nothing that smells bad in the fridge at the same time as your cold beer. If your cold beer tastes like water, a number of things could be happening and they all require slightly different solutions. Get one that's the right size for your needs, otherwise you could end up consuming too much cold beer. If both of these problem-solving tactics still result in bitter coffee, you can always try the slow drip cold brewing method.
You were excited about the first sip of the last batch of cold beer that has been stored in your fridge for the past 24 hours. The length of preparation time is the main decisive factor in this case, since the two unwanted options (sour and bitter) are at opposite ends of the processing spectrum. Understanding the principles of coffee extraction will help you to always prepare the perfect cold infusion.