The pattern suggests a french seam. That was a wonderful idea, and should avoid a bunch of stringy bits from sticking to your cold water!
My water bottle holder went together so quickly, and turned out perfectly. I think it would be a great party favor - you could change up the fabrics for any age/gender/occasion. I'm going to enlist the older boys to choose their own fabric combos in the hopes they will actually carry them (we're getting to the point where some things that I think are great are sooooo not cool).