Amazon Basics Disposable Plastic To-Go Cups and Lids, Mini, 2oz, 50 Count, BPA Free, for Condiment, Salad Dressing, Sauces, Jello Shots

I bought a bag of 2oz condiment cups for $6. Or clean them out next time you get sauces from a restaurant. They're surprisingly useful, and cheap enough to be disposable if needed. I also use these to hold water for decals, and water to wash my brushes in.