There are some “organic” spray products that you can use on the market, which are pet and ecologically-friendly. I used this product and it had reasonably good results:
EcoSmart 64 Oz. RTU 33122 Weed & Grass Killer
Model # 33122 Internet # 202102033
I too tried vinegar, bleach/water, etc. and they just came back. Finally used the above product and it worked.
The best solution, if you’re concerned about the environment, is to just pull them out manually by hand. If you’re not concerned too much, here is another product my neighbor loves:
Roundup 1 Gal. Ready-to-Use Weed & Grass Killer
Model # 5003210
I found those on the Home Depot website: www.homedepot.com