Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Hard to clean and dry out

I bought two of these for riding because they looked pretty cool. They fine as water bottles. But the problem is the clean up. The inside plastic container has 30-40 little dimples that are very difficult to dry and clean. There are also unnecessary edges/curves that also make it harder to dry out the bottle after using. Definitely a design flaw in my opinion. If you put anything other than water in these bottles be prepared to deal with mold growth both inside the bottle and in the cap. We probably have 10 other odd water bottles in our house and none of them have had these kind of problems.