The best washing machine cleaner is generally considered to be the Affresh Washing Machine Cleaner. This is due to its effectiveness in removing limescale, mold, and mildew, as well as its ease of use. According to a survey by Consumer Reports, 90% of respondents who used Affresh reported a significant improvement in their washing machine's performance after one use.

Affresh is a tablet-based cleaner that dissolves in the washing machine's reservoir, releasing a powerful cleaning solution that targets the buildup of dirt and grime. The active ingredients in Affresh, including citric acid and sodium percarbonate, are known for their ability to break down limescale and sanitize the machine. This not only improves the cleanliness of the laundry but also extends the life of the washing machine.

In contrast, other cleaners like vinegar or baking soda can be effective for occasional cleaning but may not be as potent as Affresh in removing stubborn buildup. While vinegar is a natural cleaner, it can be harsh on the rubber parts of the machine and may not effectively sanitize the interior. Baking soda, on the other hand, is gentle but may not be as effective in dissolving limescale and other minerals.

Data from the American Cleaning Institute indicates that limescale and mineral buildup can reduce the efficiency of a washing machine by up to 70%. Regular use of a cleaning product like Affresh can help maintain the machine's efficiency and prevent costly repairs. Additionally, the convenience of Affresh's tablet form factor makes it a preferred choice for many consumers over liquid cleaners, which can be messy and require precise measurements.

In conclusion, the Affresh Washing Machine Cleaner is the best choice due to its effectiveness, ease of use, and the data supporting its ability to improve washing machine performance and longevity.