I have wasted countless gallon ziplock bags when traveling - just unscrew the lids and put some plastic wrap over the opening then screw the lid back on for a much easier spill solution! (not quite as safe as a plastic bag, but a good idea!
Serious travel tip! Save yourself from suitcase/shampoo/conditioner disaster with this quick trick! where was this on my last trip home. a whole bottle of dry shampoo ALL OVER EVERYTHING! I guess better that than regular shampoo!