How can I thicken/ texturize paint with household products?

I have a painting idea that would require my acrylics (it's all I have, and I have TONS) - to be thick enough to paint on with a knife. I know there's products out there, gels etc. to use for this purpose, but I don't have the 10-15$ to obtain these products. Are there cheaper alternatives? ie. house hold products? I was thinking something like toothpaste maybe, but haven't tried it yet.