Refillable water bottles are useful park accessories. The bottles can be refilled repeatedly at water fountains to provide a healthy and frugal alternative to expensive soft drinks offered by park vendors. Some parks also have an open-door policy for DIY snacks and lunches. We've saved money by packing our own treats and meals. Rules vary by park. -------- Wisebread.com writers Sharon Harvey Rosenberg and Myscha Theriault are co-authors of the best-selling personal finance book "10,001 Ways to Live Large on a Small Budget," and founders of PoshFrugalityNetwork.com. Theriault is founder of TrekHound.com, a travel Web site, and Rosenberg is the author of "The Frugal Duchess: How to Live Well and Save Money." Find them on Twitter at Twitter.com/FrugalDuchess and Twitter.com/MyschaTheriault. -------- (c) 2010, McClatchy-Tribune News Service. Distributed by McClatchy-Tribune Information Services.