There is nothing wrong with home brews as long as they are researched. without that, you are risking significant damage to your plants. Probably someone has tried this, but on which plants? How much spray per plant? This could end up being much more costly that a product that has ben tested for safety, yours and the plant's. These ingredients are untested chemicals, and could be more toxic than something that sounds less familiar.

Ammonia ( the household liquid) is diluted ammonium hydroxide that when left to dry out lets loose ammonium molecules that are very volatile. Ammonium has bleached and killed my young tomatoes. It was produced unwantingly in a compost heap that was not securely sealed with soil and leaked into the general atmosphere of the greenhouse, thus affecting many plants. We learn't the hard way not to take any risk with ammonium. Meanwhile slugs kept on feeding on various plants next by. We still prefer to use commercial baits when it comes to maintain our ongoing commercial vegetable operation. Risk analysis is part of normal cost benefit logic.

You could sprinkle salt on them, too, but only asparagus is going to be happy with you doing that.

Caffeine is toxic to them. Unfortunately, not only is there not so much caffeine in used coffee grounds, but it is hard getting them to eat it.

Beer traps work OK but that's a waste of good beer.

This ammonia solution did more damage to my hostas than the slugs.

I have not had any plant damage. I use this on brugmansias, epiphyllums, my lemon and orange and avocado tree. The are all doing just fine. I have not used it on seedlings or unrooted plant. Sorry if it did not work for you.