Remove the screw cap on the top of a bottle of Roundup and the top of an empty plastic spray bottle.
Insert a plastic funnel into the top of the empty plastic spray bottle.
Carefully pour four parts Roundup and one part white vinegar into the funnel on the top of the plastic spray bottle. Carefully adhere to the ratio of Roundup to vinegar. An improper mix can lead to an ineffective or weakened weed killer.
Remove the funnel from the top of the spray bottle and tighten the screw cap back on top. Shake the bottle to integrate the solution.