Childhood obesity is one of the most serious public health challenges of the 21st century. While small-scale experiments change behaviors among adults in the short-run, we know little about the effectiveness of large-scale policies or the longer-run impacts due to habit formation among children. To nudge primary school children into a long-term habit of exercising, the German state of Saxony distributed sports club membership vouchers among all 33,000 third graders in 2009. In 2018, we carried out a register-based survey to evaluate the policy. Even after a decade, awareness of the voucher program was significantly higher in the treatment group. We also find that youth received and redeemed the vouchers. However, we do not find significant short- or long-term effects on sports club membership, physical activity, overweightness, or motor skills. Apparently, membership vouchers for children are not a strong enough policy tool to overcome barriers to exercise regularly.