Vinegar 5% is only slightly effective on many plants and works only in very hot dry weather.
Pickling Vinegar 9% works much better kills small plants works best in hot dry weather.
Dissolve 12 lbs. of salt in 5 gallons of boiling water. Works great in hot dry weather. Water softener salt is $5 for 50 lbs. Lowe's and Home Depot.
Pickling Vinegar plus 10% salt works better. Kills most small plants except for the large 2 ft tall weeds, thistle weed and other hard to kill large weeds.
Stomach Acid is Hydrochloric Acid = Muriatic Acid = Brick Acid. Muriatic Acid contains 60% water. Dissolve 3 lbs. of salt in 3 gallons of hot water then add a gallon of 40% strength Muriatic Acid. Kills all weeds and grass.
Muriatic Acid is $4 and up per gallon, swimming pool supply has it the cheapest.