I added beer to my chili and now it has a very bad spoiled taste! How can I fix it without tossing it out? I have tried using baking soda, but it didn't work.
I doubt you can salvage this dish. Once you add flavors you can't take them out, you can try to compensate and balance using other ingredients, which you have tried. Beer adds sweetness, bitterness from hops and sometimes acidity depending on the type of beer, you would need to judge which one you need to balance and add an ingredient to do that. However, you added baking soda, which is bitter and has a metallic taste, flavors which are unpleasant. Adding more ingredients at this point are unlikely to help, I would suggest you start again.
This answer may be too late for the batch in question, but for future reference there are some things you can try if you don't like the flavour a beer brings to a stew, though it may depend on the character of the flavour that you object to:
My experience with adding beer to cooking is that hoppier beers can lead to too much bitterness. You can attempt to counteract this with adding sweetness and/or richness.
Sweetness can be added by literally adding sugar little by little to see if that helps, but a more complex flavour may be achieved by adding more vegetables to the dish but caramelising them in a frying pan first. Onions would help with this, but also if available, root vegetables such as carrot or parsnip. Although these may not be what you would have initially chosen for the dish, they would have the additional benefit of bulking out the chilli allowing you to add a little more liquid to dilute the beer taste. Caramelising the vegetables also gives you the opportunity to add additional fats to the dish, also adding to the richness which will help de-emphasise bitterness.
Since dilution is always helpful in dealing with unwanted flavours, consider straining off some of the offending sauce and bringing the liquid levels back up with another liquid such as stock, passata or a sweeter wine. Note that as this will dilute the existing flavours you may also need to top up your spice and seasoning levels.
I'm not sure what your objective was with the baking soda and fear that that may have done more harm than good to your flavour profile.