If your kid is asking for a Stanley, they're likely responding to the massive 'cup culture' trend. The good news is that unlike most viral trends, this one is actually useful. It's a high-quality, durable tool that encourages hydration.
Just be the parent who enforces the cleaning rule. The straw and lid assembly are notorious for hiding gunk. If you're okay with a slightly overpriced (but very effective) vessel that might leak if tipped over in a bag, it's a solid buy. If you need something truly leak-proof for a chaotic backpack, look at an Owala instead.

