Maria demonstrates the effectiveness of the SOLID LAVENDER Sponge & Brush Cleanser by Beautyblender in her video review. She emphasizes that this product is the only way she cleans her beauty sponges and praises its ability to transform them from dirty to clean. Maria finds the before and after results self-explanatory, indicating that the product is easy to use and delivers noticeable results. She concludes by stating that this cleanser is the only thing one needs for sponge and brush cleaning. Overall, Maria's review highlights the product's effectiveness and convenience, making it a beneficial addition to one's beauty routine. However, she does not mention any potential drawbacks of the product.